Question

Solve the following proportion.

2/15 = 13/x

A: 390
B: 1.73
C: 2.31
D: 97.5 ***

Can someone explain why its 97.5??

Answer 1

2/15 = 13/x

Cross multiply

2 * x = 2x
15 * 13 = 195

2x = 195

x = 97.5

Answer 2

well, I would multiply both sides by 15 x

15 x (2/15) = 15 x (13/x
or
2 x = 15 * 13

x = 7.5 * 13

x = 97. 5 indeed

Now some may say just cross multiply
well ok
2 x = 15 * 13 immediately.
but I do not like the words "cross multiply" despite the fact that they are really the same thing because they are not something basic to algebra like multiply both sides by the same quantity which we know is allowed.

Answer 3

I would person ally calucate it by 13/x then times them all by 15
12/12 =10 8
And it equals 9.46