Question 282189
Substitution is pretty cool

Check this out:

{{{5x + 8y = 18}}}
and
{{{x = 6-2y}}}

are you two equations, we know what x is equal, so look at these next two things:

{{{5x + 8y = 18}}}
{{{5(highlight(6-2y)) + 8y = 18}}}

Look in the highlighted area, see how you just replace x with 6 - 2y, we did this because that is what x was equal to in the second equation

{{{5(6-2y) + 8y = 18}}}
{{{30 - 10y + 8y = 18}}} distribute
{{{30 - 2y = 18}}} combine like terms
{{{-2y = -12}}} subtract 30 on both sides
{{{y = 6}}} divide by -2 on both sides

Time to solve for X

{{{x = 6-2y}}} we know y = 6
{{{x = 6-2(6)}}}
{{{x = -6}}}

Your two answers {{{highlight(x = -6)}}} {{{highlight(y = 6)}}}