2x+8.4=2.634+5.42x round to the nearest thousandth

Given this information, which expression must represent the value of b?

You are constructing a histogram for scores that range from 70 to 100 in whole points. frequencies range from 3 to 10; that is, every whole-point score between 60 and 100 occurs at least 3 times, and at least one score occurs 10 times. which of these would probably be the best range and size for the score intervals along the x-axis?

Find the zeros of each function. f(x) = 6x^2 - 7x - 20