A dairy needs 357 gallons of milk containing 5% butterfat. How many gallons each of milk containing 7% butterfat and milk containing 1% butterfat must be used to obtain the desired 357 gallons?

area of part 1:

a1=base*height/2=(8+2)*(8-2-2-1)/2=10*3/2=15 ft^2

area of part 2:

a2=length*width=(8+2)*1=10 ft2

area of part 3:

a3=length*width=8*2=16 ft2

total shaded area : a1+a2+a3=41 ft2

total area of the reactangle : a=16*8=128 ft2

total area of the nonshaded region : 128-41=87 ft2

3x + 4y -25 =0 represents the amount of change sianna should recieve