The cost (in dollars) of x pairs of jeans at a store's regular price is modeled by the function f(x) = 40x The cost of x pairs of jeans during a sale is $5 less than 85% of the cost at regular price. What is the cost of three pairs of jeans
during the sale?
PLEASE HELP <3

9x

take the logarithm of both sides (the base of the log doesn't matter):

apply the exponent property - this says that :

distribute the log terms on both sides:

group like terms together:

divide through both sides by the coefficient on :

you can do some additional rewriting here using the properties of the logarithm to simplify things if you like: