Explanation for Question 11 From the Math (No Calc) Section on the 2020 October Sat
So question 11 is asking us to find the value of Y in the 2 system of equations above. And this question is kind of nice. 3 It tells you that you're using systems of equations. 4 So you know that you can either either use the elimination method or the 5 substitution method. I personally like to use the substitution method whenever I can. 6 And the best time to use the substitution method is when one of your 7 equations is already solved. So that only one variable is on one side of 8 the equal sign. So since we already have the Y alone, 9 it's going to be really easy to substitute the line here. 10 And we can say two X minus, 11 instead of putting Y we'll put the X plus three is equal to zero. 12 So now I'm solving for X. And if I want to solve for X, 13 I need to first distribute this negative to get rid of the parentheses. 14 And when I distributed a negative, I really just changed the sign of whatever's 15 in the parentheses. So it becomes negative X minus three is equal 16 to zero. Then I can combine like terms. 17 I have two X minus X, that's just one X. 18 And finally, I just need to remove the negative three to get X on 19 its own. And I get X is equal to positive three. 20 Right? And so you might be tempted to say, 21 C is your answer, but we can't be sure yet because we only solved 22 for X. And what we want to solve for is Y. 23 So if Y is equal to X plus three, 24 and X is equal to three, then Y is equal to three plus three, 25 which is six. So the answer for 11 is going to be D.