Answer Choices
x is y minus 1/4
x is y minus 1/2
x is y minus 1.
x is y plus 1/2
Explanation for Question 30 From the Math (Calc) Section on the Official Sat Practice Test 3
Not for question number 30, we're given some information about some variables, 2 right? B and C. And so apparently we know something about BB, 3 know something about C. And so what we can do with these top two 4 equations right here is solve them for BNC, 5 right? So this top equation, I can subtract three X from both sides and 6 I'll get that B is equal to five X minus three X minus seven. 7 And we know that five X minus three X is two X, 8 right? So this B is actually equal to two X minus seven. 9 And then we see here that see, right, I would subtract three Y from 10 both sides. C is equal to five. 11 Why am I as three Y which is two Y minus seven, 12 right? And then we're also told that B is equal to C minus 12. 13 So not only is this top equation equal to B, 14 but it's also equal to C minus 12. 15 And so what we can do at this point now is take this equation 16 for C and plug it in here, right? 17 So we'll have two X minus seven is equal to two Y minus seven 18 minus one half. 19 Right? And so we can see here that, um, 20 we've got a plus seven, we can add seven. 21 And that kind of shows us that these sevens are going to cancel from 22 both sides. So we have two X is equal to two Y minus one 23 half. Um, and so what I can do at this point now is I 24 want to find out what X is, right? Because I, 25 I want X and what I have is two X. 26 So what I'm going to do now is the vibe, both sides of my 27 equation by two. So I see that these twos cancel, 28 I get X is equal to Y and one half divided by two is 29 one, four, right? So X is one, 30 half or X is Y minus one fourth. 31 And we see that right here in answer choice. 32 A and so our best answer then is answer a.