Answer: on Saturday, she worked for 4.5 hours
Explanation:
Let x represent the number of hours that she worked after school.
Let y represent the number of hours that she worked on Saturday.
Last week, she worked for a total of 12 hours. This means that
x + y = 12
Marlee makes 5 dollars an hour working after school and 6 dollars an hour working on Saturdays. Last week she made 64.50 dollars after 12 hours of work. This means that
5x + 6y = 64.5 - - - - - - - - - -1
Substituting x = 12 - y into equation 1, it becomes
5(12 - y) + 6y = 64.5
60 - 5y + 6y = 64.5
- 5y + 6y = 64.5 - 60
y = 4.5 hours