I think when students see a problem like
this they just see so many fractions and
they immediately just say you know what
this is going to be too much trouble I
don't even want to try this I'll just
skip to the next question let's not do
that let's go ahead and think about what
we need to be able to do to be able to
solve this relatively easily now to
preface that all I simply want to do is
just create a very basic equation so you
can see where my thought process is
going to be going all right so there's
two things I want you to understand if I
had a problem like this like 12x equals
a 5 Hales this had a has a lot of
fractions too but notice here I have two
in the denominator I want to get rid of
that so how can I easily get rid of that
well I can multiply everything by two
when I multiply everything by two notice
these denominators evenly divide into
that two so therefore I'm just left with
an x + 5 right I'm sorry x equal 5 let's
do that there you go so you can see that
problem actually wasn't really that bad
multiplying by two gets rid of that
denominator but what about if I had
something like this X over 5 equals a
5es now again you could think about the
cross product I don't want to go there
right now I just want you to think now
what I need to do is I can't just pick
two because even though two divides into
two like what do I need to multiply this
by I don't want to just multiply by two
right because five does not evenly
divide by two however if I multiply it
by two and a five or two times five then
my five will divide into my five and my
two will divide in my two that is what
we call the least common multiple or the
least common denominator when you're
dealing with your denominators here so
you always want to be able to identify
that least common denominator when you
have multiple fractions now in this case
you can see that's going to be 10 and
when I multiply 10 here on both sides
I'm going to get a 2X is equal to a 25
and now you can go ahead and solve but
notice how this gave me an equation
without fractions over here for this
problem that's exactly what I want to do
now notice I do have an X and that is
going to be like the third addition here
that we have so hopefully you recognize
if I want to get the rid of the two and
the five cuz all my fractions either
have a two or five I need to multiply by
10 furthermore I also have an x on the
Teter I have to get rid of that X so I
also have to multiply everything by an
X okay so this is going to be kind of
like my fraction Buster I'm going to
multiply this by every single term if
you don't multiply by every single term
then you're not producing what we call
an equivalent equation and you have to
be able to do that right remember like
the very basics of equations whatever
you do on one side you have to do on the
other side well when you're multiplying
here by the scalar and you have terms
separated by addition or subtraction or
on both sides equations you have to make
sure you multiply everything by there
now rather than multiplying the
numerators and then dividing the
denominator in there I am going to do it
a little bit quicker I going to divide
first and then multiply so here I can
say a 5x actually you know what let's
just distribute this just so you can
kind of see I will break it down we'll
do it a little bit the slower way so you
guys can see what's happening so I have
a 10x is being multiplied by a 2 over a
5x minus Distributing that 10x * a 1
over a 2X right because we already have
the minus and that's going to be equal
to a 10x * a -2 okay so what I was
trying to show you here is 5X evenly
divides into 10x 2 times 2 * 2 is going
to give me a four over here 2 divides
into -10 that's going to be neg five
times the X's are going to divide out
and what was I at with neg five minus a
5 and then over here I have two divides
into a 10x that's going to be equal to a
5x okay so now 4 - 5 is going to be a -
1 = a 5x IDE 5 IDE 5 x = A5 which is
going to be did I forget to write the
negatives I have a oh that's a negative
oh I forgot to write this negative that
should be a Nega five there we go so
that's a negative negative so that's
going to be a positive which is answer B