Answer:
The maximum number of hours that he should spend at his job each week
are 10 hours
Explanation:
First we are going to define the variables
x: Homework's hours
y: Job's hours
How he decides that he should spend no more than 30 hours per week on the job and homework combined and the question is by the maximum number of hours that he should spend at his job, then
x + y = 30
If Roberto wants to have at least 2 homework hours for every 1 hour at his job, then
x = 2y
We solve the system of two equations and two unknowns by equalling
2y = 30 - y
3y = 30
y = 10
The maximum number of hours that he should spend at his job each week
are 10 hours
