Answer:
First evening: 8 phone calls
Second evening: 60 phone calls
Third evening: 15 phone calls
Explanation:
third evening: x
second evening: 4x
first evening: x - 7
x + 4x + x - 7 = 83
6x = 90
x = 15
First evening: x - 7 = 15 - 7 = 8
Second evening: 4x = 4(15) = 60
Third evening: x = 15