Someone explain I don’t get it

Use the x-intercept method to find all real solutions of the equation.x^3-10x^2+27x-18=0

According to a study conducted in 2015, 18% of shoppers said that they prefer to buy generic instead of name-brand products. suppose that in a recent sample of 1500 shoppers, 315 stated that they prefer to buy generic instead of name-brand products. at a 5% significance level, can you conclude that the proportion of all shoppers who currently prefer to buy generic instead of name-brand products is higher than .18? use both the p-value and the critical-value approaches.

What should be done to both sides of the equation in order to solve -5m = -40? a) multiply by -5. b) divide by -5. c) multiply by -40. d) divide by -40.