Evaluating Expressions with Two Variables | Math with Mr. J

[Music] welcome to math with mr j [Music] in this video i'm going to cover how to evaluate expressions with two variables and we have four examples that we're going to go through together in order to get this down so for numbers 1 and 2 we have a and b a equals 4 and b is going to equal 3. for numbers 3 and 4 we have x and y x is going to equal 2 and y equals ten so let's jump into number one where we have a plus b so we wanna plug in the values for those variables a equals four and b equals three and then evaluate so let's rewrite our problem with the plugged in variables so for a we need to plug in 4 plus for b we need to plug in 3. now we evaluate so 4 plus 3 gives us an answer of 7. let's go on to number 2 where we have parentheses 21 plus b and parentheses divided by a so let's plug in and evaluate so 21 plus 3 end parentheses there divided by plug in 4 for a now in this problem we have multiple operations and steps so we need to use the order of operations so any parentheses yes that's where we need to start we have 21 plus 3 in the parentheses so that's going to give us 24. bring down everything we did not use so the division sign and the 4. so we end with 24 divided by 4 which gives us 6. on to number 3 where we have x times y plus 4 squared so whenever you have a letter next to a letter or a number next to a letter it's going to be multiplication so let's plug in and evaluate so x is going to be 2 times y which is 10 plus 4 squared now we need to go through our order of operations so any parentheses no any exponents yes so that's where we start 4 squared or 4 to the second power that does not mean 4 times 2 it means 4 times 4. so that gives us 16. bring down everything we did not use and we'll go from there so we have multiplication and addition any parentheses no any exponents no any multiplication or division yes so that's what we do next we have 2 times 10 which is 20. bring down our addition and the 16 and that's where we end so 20 plus 16 equals 36 and lastly number four we have 5x plus 3y minus 30. now remember whenever you have a number next to a letter or a letter next to a letter that means multiply so plug in 5 times 2 plus 3 times 10 minus 30. so we plugged in now we are ready to evaluate so any parentheses no any exponents no any multiplication or division yes so that's where we start now we have two multiplication problems so we can work our way from left to right 5 times 2 is 10 and we'll bring down everything we did not use and now we can do the other multiplication problem 3 times 10 is 30. bring down everything else in the same exact order and now we have addition and subtraction now addition and subtraction are in the same level so to speak of the order of operations so we can work our way from left to right so let's do addition 10 plus 30 is going to give us 40. bring down our subtraction and the 30 and that's where we will end 40 minus 30 which gives us 10. so there you have it there's how you evaluate expressions with two variables plug in and use the order of operations to evaluate i hope that helped thanks so much for watching until next time peace