Hello! Remember to write complete questions in order to get good and exact answers. Here you don't provide any system so I couldn't help you in an exact way, but in a general manner. When solving systems by graphing we just need to find the points of intersection of the graphs of the functions that built up the system.
Suppose you have the following system of linear equation:
yBy using graphing tools, we get the graph shown below. As you can see, the point of intersection of both lines is
Explantation: 5 pineapples is going to be multiplied by p, the cost of 1. And 3 mangoes are going to be multiplied by q, the cost of 1. And adding the two totals together gives you the total cost.