Explanation for Question 11 From the Math (Calc) Section on the Official Sat Practice Test 6
Question 11 gives us these two expressions. 2 We have seven X plus three, Y is equal to eight and six X 3 minus three. Y is equal to five and it asks us for the solution 4 X, Y to the system of equations above what is the value of X 5 minus Y. So to answer this question, 6 we first have to find the solution X, 7 Y to the system of equations. 8 So let's write these equations off to the side. We've got seven X plus 9 three Y equal to eight, 10 and we have six X minus three, Y is equal to five. 11 The easiest way to solve this one is going to be elimination. 12 So that's when you essentially subtract one expression from another, 13 or add the two equations together to cancel out one of the variables. 14 So in this case, we have seven X plus six X is equal to 15 13 X. 16 And then I knew to do elimination because you see that this three Y 17 when you add the second expression to it, 18 we get three Y plus negative three Y. 19 So that's equal to zero Y so just equal to zero. 20 And then we have eight plus five is equal to 13. 21 So now we have 13, X is equal to 13. 22 So we have X is equal to one. And now with that, 23 we can plug it back in to either of the original equations to solve 24 for Y so plug X into either equation and then solve for Y I'm 25 going to plug it into the first, just because it's the first one on, 26 um, of our two equations. So Sanex plus three, 27 Y is equal to eight. Since we know that X is equal to one. 28 So plugin one here, we have seven times one plus ...