Samuel is mixing different-color paints for a mural he has been asked to paint in the school gymnasium. To create the color purple he wants, Samuel mixes r gallons of red paint with b gallons of blue paint. Red paint costs $25 per gallon and blue paint costs $22 per gallon. He also needs $65 to spend on paint supplies. Samuel knows the cost of his paint and supplies can be found using the expression 25r + 22b + 65. Help!!!