Question

SUBSTITUTION METHOD
8x+4y=15
x+y=3

Answer 1

x = 3/4 and 9/4

Explanation:

Rewrite equations:

x+y=3;8x+4y=15

Step: Solvex+y=3for x:

x+y=3

x+y+−y=3+−y(Add -y to both sides)

x=−y+3

Step: Substitute−y+3forxin8x+4y=15:

8x+4y=15

8(−y+3)+4y=15

−4y+24=15(Simplify both sides of the equation)

−4y+24+−24=15+−24(Add -24 to both sides)

−4y=−9

`(-4y)/(-4) =(-9)/(-4)`

Step: Substitute
`(9)/(4)` for y in x=−y+3:

x=−y+3

x = -
`(9)/(4)` +3

`x=(3)/(4)` (Simplify both sides of the equation)

Answer:

`x=(3)/(4)` and
`y=(9)/(4)`

Answer 2

(2.25, 0.75)

Explanation:

x+y=3

subract x from both sides

y=x-3

subsitute y

8x+4(x-3)=15

distribute

8x+4x-12=15

combine like terms

12x-12=15

12x=27

divide

x=9/4 or 2.25

Substitute in one equation

2.25+y=3

y=0.75 or 3/4

Don't forget to check your work!