Pricing fruits

Question

A fruit stand prices bananas,tangerines,oranges,grapefruit,and apples by the piece- not by weight. If 3 bananas and 8 apples cost $2.50,and if 7 bananas and 12 apples cost $4.00,how much do 10 bananas and 20 apples cost?

Answer 1

Solve for the variables using these two equations

 3b + 8a = 2.50           7b + 12a = 4.00