one day a plumber received $120 for working 2 hours. the next day he worked 8 hours and earned $390. find the amount the plumber earns per hour.
His hourly pay is the slope of the line, which is
(390-120)/(8-2) = 45
Looks like the plumber's pay consists of a flat rate plus an hourly charge.
let
pay = rate*t + b , where t is the number of hours worked
120 = 2t + b
390 = 8t + b
subtract them:
6t = 270
t = 45
subbing back, b = 30
He earns $45 per hour, and the pay equation is
pay = 45t + 30.00
check:
if t = 2, pay = 45(2) + 30 = 120
if t = 8, pay = (45)(8) + 30 = 390
my answer is correct