The answer to the problem is 5.
You would spend 25 minutes on the elliptical trainer, and 15 minutes on the stationary bike.
An arithmetic sequence is a pattern of numbers that increase or decrease at a constant amount.
XZ ~ UW
UV ~ XY
VW ~ YZ
Take any corresponding side and the ratio of it is your answer.
Example :
XZ / UW = 14/ 2 = 7
XY / UV = 21 / 3 = 7
YZ / VW = 28 / 4 = 7
Therefore, your answer is B. 7