Comparing functions word problems

Question

David tutors elementary students on the weekend. The total bill for 1 hour is $40. The total bill for 3 hours is $90. What is the David’s flat rate as a tutor? Show your work!

Answer:

what would the answer be

8th grade math

Answer 1

y = mx + b

40 = m(1) + b

-(90 = m(3) + b)

-50 = -2m

m = 25

He charges 25 per hour and 15 to walk in the door.