A machine shop employee earned $642 last week. She worked 40hours at her regular rate and 9 hours at

A machine shop employee earned $642 last week. She worked 40hours at her regular rate and 9 hours at a time and a half rate. Find her regular hourly rate.

Let the regular hourly rate be h. We're given:
40h + 40(1.5)(h - 40) = 642

Multiply through and simplify:
40h + 60h - 2400 = 642
100h - 2400 = 642

To solve for h, we type this equation into our search engine and we get:
h = 30.42