Given
Jeb has to pay his plumber $65 to come to his house and $40 per hour
jeb paid him $325
Find out how many hours did the plumber work
To proof
let the number of hours plumber work be x
Jeb has to pay his plumber $65 to come .
extra pay per hour = $40 per hour
total jeb paid = $ 325
than the equation becomes
65 + 40x = 325
now solving the equation
40x = 325 -65
40x = 260
x = 6.5 hour
6.5 hour plumber did the work.
Hence proved