Explanation for Question 19 From the Math (No Calc) Section on the Official Sat Practice Test 4
Now for number 19, we're trying to find the value of X it's. 2 Something important to know is that these systems of equations problems can be relatively 3 long, right. But in order to, 4 um, to make these faster, what we really want to do here is get 5 rid of the Y uh, Y values. 6 So if we're using, um, what's the word substitution you want to 7 solve for Y and plug in, Y which in this case is what I 8 think we're going to do, because looking at these two equations, 9 I'm going to have to multiply both equations by numbers in order to get 10 elimination to work. So that's probably a pretty long process, 11 but if I take this equation, it shouldn't be too hard to solve it 12 for Y all I need to do is subtract six X from both sides. 13 So Y is on its own. And then I can divide everything by three 14 to get rid of the three that's attached to the Y and everything divides 15 out very nicely. 16 I got negative two X plus five. 17 So now I'm going to take that and pull that into my top equation. 18 So get negative three X plus four, 19 but instead of writing, Y I'll write the negative two X plus five that 20 I just solved for, and that is still equal to 20. 21 So to simplify, I'll distribute the four and get negative three X minus 22 eight X coalesced 20 is equal to 20. 23 Um, and so, you know, now we see 20 twice. 24 So maybe if you have a little bit of intuition about how this will 25 go, you could stop here and write your answer. Well, 26 let's go ahead and go all the way. Let's...