If efgh is a rectangle, what is fh?

Find the missing number. a. 3 : 24 = : 72 b. : 18 = 5 : 9 c. 6: = 36 : 36

I’m stuck on this equation, anyone got the answer?

List x1, x2, x3, x4 where xi is the left endpoint of the four equal intervals used to estimate the area under the curve of f(x) between x = 4 and x = 6. a 4, 4.5, 5, 5.5 b 4.5, 5, 5.5, 6 c 4.25, 4.75, 5.25, 5.75 d 4, 4.2, 5.4, 6