Answer: 8 lawns
Explanation:
Since he budgets 13 a week, do 200+13 to get 213. This is how much he needs to earn from mowing lawns to get rid of his budgeting that week. Now divide 213/30 and you get 7.1. Since he cannot do part of a lawn, you round up to 8. He must mow 8 lawns in one week to earn $200 in that week.
No idea why it says system of equations.