Explanation for Question 9 From the Math (Calc) Section on the 2017 May Sat
Question nine says the sum of two different numbers, 2 X and Y you're 70. And the difference when the smaller number is subtracted 3 from the larger number is 30. What is the value of X times? 4 Y I'm going to highlight the last thing right here, 5 value of X plus Y times Y. So we remember we're not solving for 6 X, we're not solving for Y as our final answer we're solving for X 7 times. Y um, it's easy sometimes to forget that and answer, 8 um, whatever you got for the first grade variable and not follow through with 9 the problem. So let's make sure we remember to so all the way through 10 now, they give us two equations here, 11 essentially, and we just have to do system of equations. 12 First equation we can get from here. The sum of the two numbers 13 X and Y is 70. So we just have X plus Y equals 70. 14 And then the difference when the smaller number is retracted from the larger number 15 is 30. So smaller number, 16 um, subtracted from the larger number. 17 Doesn't matter which one you choose. Um, 18 I'm going to say, why is the bigger one minus X equals 30. 19 Now we just solve. Um, 20 first step in solving for system of equations is getting one equation to be 21 equal to one variable or solving one equation for one variable. 22 I'm going to work with this one. Um, 23 and we can just say, Y equals 30 plus X. 24 The second step in system of equations, 25 um, is I'm going to write a line here so that you noticed the 26 different one. The second step and system of equati...