Well this is a hard question to answer, but this is how i would put it.
You would take a number (lets use 15) and the second number (lets use 5) would determine how many times it would go into 15. In other words, 5 time x would equal 15 (5x=15). 5, being a factor of 15, would evenly fit into 15 three times.
diameter (d) = 2 · r
Circumference (C) = 2 π · r → C = π · d → d = 
1985year ->275cell phones->100%
1994year -> x cell phones ->100%+360%
40% • (1994-1985)= 40% • 9= 360%
275 cell phone 100%
X cell phones. 100+360%=460%
x=275•460%/100%
x=12420/100
x=1265
99% sure this is a correct answer
x=275 • 460%/100%
x=12,420/100
x=1265
1994-1985= 9 yrs • 40%= 360%
Answer:
C; None of the above.
Step-by-step explanation:
Pretend x=1, y=0, and z=2.
You have to match an answer to 1+0-2 (equals to -1).
The first equation would be 2+0+1. When you add them all together you get 3, and that isn't equivalent to -1, so therefore this one is not the answer.
The second equation becomes 1+2+0, and when you solve for the answer, you see that the answer is also 3, and so we can conclude that neither A or B matches with the equation above, so the answer is C, None of the above.