Question

Shawn earns $3.50 per hour for the first 40 hours worked in a week and $20.25 per week, for hours over 40. If he earns $661.50 in one week, how many hours did he work?

Answer 1

You appear to have a typo
You must have meant:
$20.25 per hour for overtime.

normal weekly wage
= 40(3.50)
= 140
leaving 661.50-140 or $521.50 for overtime.
overtime hours = 521.5/20.25 = 25.75

So he worked 40 + 25.75
or 65.75 hours.

strange question: very huge gap between regular rate and overtime rate