What is the system of inequalities that would represent this graph and how would it be found

Kelly sells magazine subscriptions after work. The half-year subscriptions cost $12, and the full-year subscriptions cost $20. Today, Kelly has 20 subscription cards with her, only one subscription can be ordered on each card, and she wants to sell subscriptions totaling at least $300.If the solution region represents the amount of half-year and full-year magazine subscriptions Kelly needs to sell to reach her goal, which graph's shaded area represents the solution region?

I'm trying to graphically determine the solution set for the system of inequalities. Could you please help me understand how to calculate this and show on a graph x+y >= -3 3x - y <= 7