Answer:
9 hours
Step-by-step explanation:
He earns 11 for every hour,
11/1
And he earned 99, but we don't know how many hours
99/x
Set the expressions equal to each other
11/1=99/x
Cross multiply
11x=99
Divide by 11 on both sides
x=9
So he worked 9 hours
Hope this helps! :)
