To figure this out, all we need to do is some simple division. First, let's divide the $30 we want to earn per week by the $6 per hour and the $3 per hour we'll earn doing each of those jobs.
30 ÷ 6 = 5
30 ÷ 3 = 10
Now, let's see how much money we'd earn if we worked both jobs for 6 hours.
6 * 6 = 36
3 * 6 = 18
There we have it, if we worked both jobs 6 hours each, a total of 12 hours per week, we'd make $54.
Here's your answer:
Working a total of 12 hours a week, 6 hours at the grocery store, 6 hours mowing lawns, you can make $54.00 per week.
Hope this helped you out. :)