Calculate 3ab + b for a=2 and b=-3

The u-drive rent-a-truck company plans to spend $13 million on 320 new vehicles. each commercial van will cost $25 comma 000, each small truck $50 comma 000, and each large truck  $80 comma 000. past experience shows that they need twice as many vans as small trucks. how many of each type of vehicle can they buy?

For f(x) = 3x+1 and g(x) = x2 - 6, find (g/f)(x)

What is the inverse of f(x) = 6x -24