Question

Solve the system of linear equations by substitution.

x + 4y = 21
y = −x + 12
the solution to the system is ( , ) answer is an ordered pair

Answer 1

Answer: (9,3)

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Step-by-step explanation:

We can replace y in the first equation with -x+12 due to the second equation.

x+4y = 21

x+4( y ) = 21

x + 4(-x+12) = 21

x-4x+48 = 21

-3x = 21-48

-3x = -27

x = -27/(-3)

x = 9

which leads to,

y = -x+12

y = -9+12

y = 3

Therefore, the solution as an ordered pair is (x,y) = (9, 3)

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Check:

x+4y = 21

9+4(3) = 21

9+12 = 21

21 = 21 .... the first equation works

and,

y = -x+12

3 = -9+12

3 = 3 ... so does the second equation

Both equations are true for those x and y values. The answer is fully confirmed.