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

2 Answers

4 votes

Answer:

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)

User Palash Kosta
by
7.8k points
5 votes

Answer:

(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!

User NaveenBharadwaj
by
8.7k points

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