Let be the number of hours he rakes leaves.
The the amount of makes from cutting grass is dollars and the amount of money he makes from raking leaves is dollars
He cannot work for more than 15 hours, thus:
there's your first inequality, simple huh?
he wants the amount of money he makes to be at least (that means "greater than or equal to") 120 dollars, thus:
there's your second inequality. that wasn't so bad. now get to graphing, and shade the region that satisfies both inequalities