Question

Over the last three evenings, Yoko received a total of 73 phone calls at the call center. The third evening, she received 3 times as many calls as the first evening. The second evening, she received 7 fewer calls than the first evening. How many phone calls did she receive each evening?

Answer 1

The first evening she received x calls.
The second evening she received 7 fewer calls than the first evening, so she received x-7 calls.
The third evening she received 3 times as many calls as the first evening, so she received 3x calls.
Over the three evenings she received 73 calls altogether.

$x+x-7+3x=73 \\ 5x-7=73 \\ 5x=73+7 \\ 5x=80 \\ x=\frac{80}{5} \\ x=16 \Leftarrow \hbox{the first evening} \\ \\ \hbox{the second evening:} \\ x-7=16-7=9 \\ \\ \hbox{the third evening:} \\ 3x=3 \times 16=48$

The first evening she received 16 calls, the second evening she received 9 calls, the third evening she received 48 calls.