Answer:
Number of calls received in 1st evening = 24
Number of calls received in 2nd evening = 33
Number of calls received in 3rd evening = 72
Step-by-step explanation:
Let
number of calls received in first evening be "x"
number of calls received in 2nd evening be "y"
number of calls received in 3rd evening be "z"
Total, in 3 evenings, we have 129 phone calls, so we can write:
x + y + z = 129
3rd evening, 3 times as first evening. We can write:
z = 3x
2nd evening, 9 MORE THAN FIRST. So we can write:
y = 9 + x
Now we replace 2nd and 3rd equation in 1st equation to get:
x + y + z = 129
x + 9 + x + 3x = 129
Now, first, we solve for x:
Solving for y:
y = 9 + x
y = 9 + 24
y = 33
Solving for z:
z = 3x
z = 3(24)
z = 72
Thus,
Number of calls received in 1st evening = 24
Number of calls received in 2nd evening = 33
Number of calls received in 3rd evening = 72