How do you solve $5x+y=15, 2x+y=12$ using substitution?

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Answer 1 · 2016-12-12T13:54:38

$x = 1$ and $y = 10$

Step 1) Solve the first equation for $y$ :

$5x - 5x + y = 15 - 5x$

$0 + y = 15 - 5x$

$y = 15 - 5x$

Step 2) Substitute $15 - 5x$ for $y$ in the second equation and solve for $x$ :

$2x + 15 - 5x = 12$

$-3x + 15 = 12$

$-3x + 15 - 15 = 12 - 15$

$-3x + 0 = -3$

$-3x = -3$

$(-3x)/-3 = (-3)/-3$

$x = 1$

Step 3) Substitute $1$ for $x$ in the solution to the first equation in Step 1) and calculate $y$ :

$y = 15 - (5*1)$

$y = 15 - 5$

$y = 10$

How do you solve 5x+y=15, 2x+y=125x+y=15, 2x+y=12 using substitution?