SOLUTION: solve system of equations by substitution 4x+y=28 y=3x i know you change it to: y=-4x+28 y=3x but i am stuck from there...

Question 798950: solve system of equations by substitution
4x+y=28 y=3x
i know you change it to:
y=-4x+28 y=3x
but i am stuck from there...
Answer by Finavon(81) (Show Source): You can put this solution on YOUR website!
4x+y=28 (1)
y=3x (2)
replace/substitute y in (1) with the value in (2)
(1) becomes 4x + (3x) = 28
adding the xs together gives
7x = 28
dividing both sides by 7 gives

or x = 4
enter this value in (2)
y=3*4 = 12
Check by putting both values in (1):
4*4+12 = 16+12 = 28

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