A dealership paid $8,000 for a car at an aucton. A salesman at the dealership sold
the car for 40%, more than the auction
price. If he recelved a 157 commission on
the difference between the auction price
and sales price, what was his commission?

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: