Question

Flour costs $0.80 per pound and sugar costs $0.50 per pound. An order of flour and sugar weighs 15 pounds and costs $9.00. How much flour and sugar is there?

Answer 1

Let's solve your system by substitution.

x+y=15;0.8x+0.5y=9

Step: Solvex+y=15for x:

x+y=15

x+y+−y=15+−y(Add -y to both sides)

x=−y+15

Step: Substitute−y+15forxin0.8x+0.5y=9:

0.8x+0.5y=9

0.8(−y+15)+0.5y=9

−0.3y+12=9(Simplify both sides of the equation)

−0.3y+12+−12=9+−12(Add -12 to both sides)

−0.3y=−3

−0.3y

−0.3

=

−3

−0.3

(Divide both sides by -0.3)

y=10

Step: Substitute10foryinx=−y+15:

x=−y+15

x=−10+15

x=5(Simplify both sides of the equation)

Answer:

x=5 and y=10