The number of fish in a lake decreased by 20% between last year and this year. Last year there were 75 fish in the lake. What is the population this year?

Simply 8x squared + 5(7x squared- x) - 2x =

On a string instrument, the length of a string varies inversely as the frequency of its vibrations. an 11-inch string has a frequency of 400 cylces per second. find the frequency of a 10-icnch string.

In triangle △abc, ∠abc=90°, bh is an altitude. find the missing lengths. ah=4 and hc=1, find bh.