Carson runs a farm stand that sells strawberries and bananas. Each pound of strawberries sells for $3 and each pound of bananas sells for $1.50. Carson sold 4 times as many pounds of strawberries as pounds of bananas and he made $135 altogether. Graphically solve a system of equations in order to determine the number of pounds of strawberries sold, x, and the number of pounds of bananas sold, y.