Answer:
See below.
Step-by-step explanation:
Total = 110
Let calls on third evening = x
second evening = 4x
first evening = x + 8
=> x + 4x + x + 8 = 110
=> 6x = 102
=> x = 17
First evening = x = 17 calls
Second evening = 4x = 68 calls
Third evening = x + 8 = 25 calls
You would have to add x1 + x2 and divide by 2. do the same with y1 and y2.
(1/2,-1/2)
30+5=5+30 with commutative property or 30+5=35
