Answer:
Billy earns approximately 44 dollars in a week.
Explanation:
Set up a percentage proportion, 45/100 = 20/x.
Cross multiply 100*20 and 45*x
100*20=2000
45*x=45x
Then divide both sides by 45.
45x/45=x and 2000/45=44.444444444444444444444
Therefore x ≈ 44