You have two jobs. one job pays $7 per hour and the other pays $8.25 per hour. you worked 22 hours total last week and earned $171.50. how many hours did you work at each job?

X = 1st job
y = 2nd job

x + y = 22x = 22 - y
7x + 8.25y = 171.50

7(22 - y ) + 8.25y = 171.50
154 - 7y + 8.25y = 171.50
-7y + 8.25y = 171.50 - 154
1.25y = 17.50
y = 17.50 / 1.25
y = 14 <== 14 hrs at the 8.25 per hr job

x + y = 22
x + 14 = 22
x = 22 - 14
x = 8 <=== 8 hrs at the 7 per hr job

Subtracting is the opposite of adding