Explanation for Question 1 From the Math (No Calc) Section on the 2018 April Sat
Question one asks according to the system of equations above what is the 2 value of X. So to figure this out, 3 I'm going to start by taking this topic equation and I'm going to set 4 it equal to Y so X plus Y is equal to 21. 5 Well, if you subtract X from both sides, 6 you get, Y is equal to 21 minus X, 7 and now we can take that value for Y and plug it in, 8 in this bottle equation. So X minus two times 9 21 minus X is equal to negative three. 10 Next we can factor this. So X plus negative 42 11 plus two X is equal to negative three. 12 And if we add and subtract like terms, we get three X is equal 13 to, if we add 42 to both sides, 14 45, finally, 15 we can divide both sides by three and get X is equal 16 to 15, which is our final answer. 17 So we know that D is the current.