A student has started a lawn care business. He charges \$15$15​ per hour to mow lawns and \$20$20​ per hour for gardening. Because he is still in school, he is only allowed to work at most 2020​ hours per week. His goal is to make at least \$300$300​ per week.
a) Create a system of equation or inequalities that models the situation. Define the variables you use.