Explanation for Question 19 From the Math (No Calc) Section on the 2019 October Sat
Now a number 19, what we have here is a systems of equations and 2 we're trying to solve for X. And this system is actually really set up 3 for us to solve for X rather quickly, 4 using the process of elimination. 5 If we look at how this is set up, and we think about what 6 elimination means, right? Adding two equations together, 7 we can see that if we add these to the plus Y and the 8 minus Y are going to cancel out immediately. 9 So let's go ahead and do that, right? Let's add down X plus X 10 is two X positive Y minus Y. 11 Those cancel to give us zero and then two plus three that's five. 12 So now we have a brand new, easy to solve equation that only has 13 X as the variable and all this left as attached to the X is 14 a two. And to get rid of that too, I need to now divide 15 by two. So I'll divide both sides of my equations by two, 16 and I get the X is equal to five Habs. 17 And so that's going to be our answer, right? Or you could write it 18 as 2.5. Um, keep in mind this isn't the only way to solve the, 19 uh, the problem. You could also use substitution. 20 And if you were to use substitution, your final equation would also look like 21 this two X minus two X is equal to five, 22 but it's going to be a lot faster to use elimination in this case.