Answer:
D = a*t + b*(T-t)
Explanation:
In the example given, four variables are to be considered here,
How many dollars he makes per hour , same as how many dollars he makes as a waiter, How many hours he worked both as tutor and a waiter
Let define our variables
let a = the amount of dollars he makes per hour as a tutor
Let b = the amount of dollars he makes as a waiter
Let t = number of hours he worked as a tutor
Let T = the total hours combined he worked both jobs in a month
Therefore, T-t = number of hours left he worked as a waiter.
Then, D = total dollars Frank received this month in which is: D = a*t + b*(T-t)