Hello forum Vaironl here, I have to solve some equations using two methods.

1 Substitute x and then solve for y.

2 Solve for y and then substitute x.

Here is my first problem I can do the first method but I don't understand exactly how to solve the second method.

$\displaystyle \4x+& 9y& =30& ; x=3$

For the first method I got

12+9y=30 =

9y=18 =

y= 2