your expression: 25+10x
#2: 25 + 10x = 75
10x = 75-25
10x = 50
10x/10 = 50/10
x = 5
The customer can download 5 gigabytes at the most
Linear equality:
25+10x (plug in the 5 into the x, for x = 5)
25 + 10(5) = 75
then plug in 1 - 5 (since you can only download 5 at the most)
that is your linear
hope this helps