Answer:
 less than 4.7 gigs
Step-by-step explanation:
The cost of Janelys's cell phone plan will be the sum of the flat cost and the product of the per-gig cost and the number of gigs of data she uses.
 y = 46.50 +5g
She wants this to be less than $70 per month, so we can find the constraint on her data usage from ...
 46.50 +5g < 70
 5g < 23.50 . . . . . . . . subtract 46.50
 g < 4.7 . . . . . . . . . . divide by 5
Janelys must use less than 4.7 gigs of data to stay within her budget.