What is the percent of decrease from 40 to 30?

Given f(x)= 9x+1 and g(x)=x^3, choose the expression (f*g)(x)

Reduce fractions expressing probability to lowest terms. in 3,000 repetitions of an experiment, a random event occurred in 500 cases. the expected probability of this event is?

Tom can paint the fence in 12 hours, but if he works together with a friend they can finish the job in 8 hours. how long would it take for his friend to paint this fence alone?