Lia gets paid $45 an hour plus $150 each week. She hopes to earn at least $690 this week.

Assuming the question is:
 "How many hours does she have to work to reach her goal of $690"

That information can make the equation: 
money earned in a week = 45h + 150

We then sub in $690
690 = 45h + 150
Rearrange to find h
540 = 45h
12 = h

Lia has to work 12 hours to earn at least $690