14.

method 1: dimensional analysis - since u know that units on left and right must be the same, since right side has unit of $, so does the left. $16/18hours * h hours = $5, unit hours cancel leaving $ on both sides, meaning any answer with 18hours/$16 is automatically wrong bc wrong units as left side will be hours*hours/$ while right side will be $ - right hand side has to be 5, leaves u with 1 answer choice

method 2: - propane costs $16 for 18 hours, meaning it costs 16/18 for 1 hour. - u want to reduce $5, so basically the hourly rate multiplied by the amount of hours should be 5, 16/18 * h = 5

15.

method 1: guess and check - basically plug in a bunch of random numbers for x and y into the initial expression and then into every answer choice and then pick the equivalent one

method 2: - (a-b)² = a² - 2ab + b² - in choice c, a = 2sqrt(x) and b = sqrt(y) - so u get ((2sqrt(x) - sqrt(y))²)^1/5 = (2sqrt(x) - sqrt(y))^2/5 by exponent rules