Answer:
One job that pays $8 worked 12 hours.
Other job that pays $10.50 worked 18 hours.
Explanation:
x = hours worked at 8.00
y = hours worked at 10.50
x + y = 30
8x + 10.50y = 285
Solve the first equation for x.
x + y = 30
x = 30 - y
Substitute 30 - y for x in the second equation.
8x + 10.50y = 285
8(30 - y) + 10.50y = 285
240 - 8y + 10.50y = 285
-8y +10.50y = 285 - 240
2.5y = 45
y = 18
x = 30 - y or 30 - 18
x = 12
Check:
x + y = 30
18 + 12 = 30
30 = 30
8x + 10.50y = 285
8(12) + 10.50(18) = 285
96 + 189 = 285
285 = 285