How do you do this? i don't get it? this is hard for me to solve

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

What is the 12th term of b(n)=-4-2(n-1)

2.5 milligrams is equivalent to how many grams