# How do you solve by substitution  x + y = 11 and x - y = 1?

The first step would be to write $x - y = 1 \rightarrow x = 1 + y$
and then to replace $x$ by $1 + y$ in $x + y = 11$
thus $1 + y + y = 11 \rightarrow 2 y + 1 = 11 \rightarrow 2 y = 10 \rightarrow y = 5$
Now back to $x - y = 1$ with $y = 5$
$x - 5 = 1 \rightarrow x = 6$