Hi there! :)
Answer:

m∠BGC = 16x - 4
m∠CGD = 2x + 13
m∠BGC + m∠CGD sums up to 90°, therefore:
(16x - 4) + (2x + 13) = 90
Combine like terms and simplify:
16x + 2x - 4 + 13 = 90
18x - 4 + 13 = 90
18x + 9 = 90
18x = 81
18x/18 = 81/8
x = 4.5
X-15+9-4=x-10 there are ten fewer people after the second stop than the original amount
You would start by saying his budget is $80 so you start with 80= he pays an initial fee of $59.50 every month plus $5 per gigabyte so you would set it up like
80=59.50+5x
X being how many gigabytes he uses then you solve 80-59.50 is 20.5 divided by 5 gives you 4.1 but you round down cause you don’t want to pass the limit so therefor the most gigabytes he can use is 4
4x / 5 = 1 / 3 ( 2x - 15 )
4x / 5= ( 2x - 15 ) / 3
4x × 3 = 5 ( 2x - 15 )
12x = 10x - 75
12x - 10x = - 75
2x = - 75
x = - 75 / 2
x = - 37.5