How do you solve by substitution $y = 3x + 5$ and $4x – y = 5$ ?

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Answer 1 · 2015-06-07T07:22:19

We can substitute the expression for $y$ given to us by the first equation into the second equation:

$5 = 4x-y = 4x-(3x+5) = 4x-3x-5$

$= (4-3)x-5 = x-5$

Then add $5$ to both ends to get:

$x = 10$

Then substitute this value of $x$ for $x$ in the first equation:

$y = 3x+5 = 3*10+5 = 30+5 = 35$

How do you solve by substitution y = 3x + 5y = 3x + 5 and 4x – y = 54x – y = 5?