Two sisters want to save money to buy a game. The game costs $90. One sister has $36 and the other has $40. How much more money do they need?

you didn't post any answer choices, so its not 100% clear what your teacher is looking for

however, log(15/7) is equivalent to log(15) - log(7)

i'm using the rule log(x/y) = log(x) - log(y)

i'm assuming that it's c.)   volcanoes built the mountains and earthquakes tore them down.