# How do you solve 2a=8 and a+b=2 using substitution?

If $2 a = 8 \to a = \frac{8}{2} = 4$
In the second expression we may replace $a = 4$
$\to 4 + b = 2$ now subtract $4$ on both sides:
$\to \cancel{4} - \cancel{4} + b = 2 - 4 \to b = - 2$