The following triangles are similar. Which of the proportions could be used to solve for x:

21

35
X
15

30

12

T

15

A

35

21

15

T

B

35

21

<

C

D

30

15

35

The proportions that could be used to solve for x are:

A:

21/35 = X/15

B:

35/21 = X/15