From the table :
Lin worked for 5 hours and earned 90$
LIn worked for 1 hour and earned 18$
Lin worked for 8 hour
so the earning is

Lin worked for 8 hours so the earning is 144$
If lin works for 3 hours then the earning is
So the answer for 3 hours is 54$.

If lin works for 21 hours then the earning is

so the answer for 21 hours is 378$.