Answer:
Greg could trim trees anywhere more than 7.67 hours for more than $50.
Explanation:
First, set up the equation. Since he doesn't have a fixed number of dollars to earn (it is more than $50, not just $50), this would be an inequality.
50 < 6t - 4
50 is the principle goal, 6t because t is hours, and he gets $6 every hour, and - 4 because he pays a one time fee for equiment.
Then, you solve the inequality the way you would with one-variable inequalities:
50 < 6t - 4
46 < 6t
7.67 < t