Alex works as an office clerk and his office job pays him $11 per hour. monica works as a cashier and her job pays her $12.75 per hour. together, they worked 45 hours and earned a total of $530.
how many hours did monica work in her job?
a.
20
b.
25
c.
30
d.
35

Alex_Hours + Monica_Hours = 45
Alex_Hours * 11 + Monica_Hours * 12.75 = 530

From the first equation:
Alex_Hours = 45 - Monica_Hours

Substituting into the section equation gives:
(45 - Monica_Hours) * 11 + Monica_Hours * 12.75 = 530
495 - Monica_Hours * 11 + Monica_Hours * 12.75 = 530
Monica_Hours * 12.75 - Monica_Hours * 11 = 530 - 495 = 35
Monica_Hours * (12.75 - 11) = 35
Monica_Hours * 1.75 = 35
Monica_Hours = 35 / 1.75 = 35 / (7 / 4) = 35 * 4 / 7 = 5 * 4 = 20

Monica worked 20 hours -- Answer A.

What mathematical statement is missing ? ? the answer is b