Does −(×)=(−)×(−) explain??

Which function has an inverse function? a.f(x)= |x+3|/5 b. f(x)= x^5-3 c. f(x)= x^4/7+27 d. f(x)= 1/x²

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?

Varies inversely with x. if y=8.5 when x=-1 find x when y=-1