For this one, plug in your <em>x </em> and <em>y</em> intercepts for the corresponding letters and see which one is true. I always start with the first equation and then see which ones solve it first, that will cut your time down on a test.
Lets start with A. (4,5)
and the first equation y=x+1
5=4+1, which is true so A is a potential answer
B. (2,3)
3=2+1, B is a potential as well
C. (-2,1)
1=-2+1, which is false so C is out
D. (-4,-3)
-3=-4+1, which is true.
To cut down on time, do the same thing with the second equation and your final answer will be A. (4,5)
3s = 72 (Multiply 8 both side).
s = 24 (divide by 3 both side)
24 students
So, 
Simplified as mixed number equals to
(
Keep in mind that the LCM was 8.)
28oz $2.24
2.24/28 = .08
1.20/12 = .1
3.60/40 = .09
As you can see 2.24 for 28oz has the cheapest unit cost at .08 per oz.
