3 GBs per month because you have to take 30-21 (the monthly cost of the phone)=9 and each GB is $3 a month so 9 divided by 3= 3
Answer is in the photo. I can't attach it here, but I uploaded it to a file hosting. link below! Good Luck!
tinyurl.com/wpazsebu
Domain is all the possible inputs of an equation. In this example, the only concern is the x + 5 because the denominator cannot equal 0 because we can't divided by 0. So we set x + 5 equal to zero and solve for x.
x + 5 = 0
x = -5
The restriction is that x cannot equal -5.