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