What do i do when you have a question like "y-1=4/5(x+15)" i have no idea what to do next!

Given the equation f(x)=a(b)x where the initial value is 40 and the growth rate is 20% what is f(4)

Kyle and elijah are planning a road trip to california. their car travels 3/4 of a mile per min if they did not stop driving, how many miles could kyle and elijah drive in a whole day? ? 1 day = 24 hours. plzzz i will give you 100 points

Mon wants to make 5 lbs of the sugar syrup. how much water and how much sugar does he need… …to make 5% syrup?