How do I figure this out?

Cherie measures and records the lengths and sizes of the same style of a sandal found at a shoe store. which equation can be used to determine the approximate shoe size, s, for a foot length of x inches? s = x – 2 s = 2x – 10 s = x + 6 s = 2x + 4

How long must $542 be invested at a rate of 7% to earn $303.52 in interest? in a easier way

What is always true when two whole numbers are subtracted?