Isuck at everything and this class gives me panic attacks

What are the values of each variable in the diagram below?

If 30 lb of rice and 30 lb of potatoes cost ? $27.60? , and 20 lb of rice and 12 lb of potatoes cost ? $15.04? , how much will 10 lb of rice and 50 lb of potatoes? cost?

The difference of two numbers is 40. find the numbers if 0.3 parts of one number is equal to 37.5% of the other one.