Isolate the x. Add 2x to both sides, and 4 to both sides
x (+2x) -4 (+4) = -2x (+2x) + 9 (+4)
x + 2x = 9 + 4
3x = 13
Divide 3 from both sides
3x/3 = 13/3
x = 13/3
hope this helps
