remember yo can do anything to an equation as long as you do it to both sides
so
remember distributive property
a(b+c)=ab+ac
so first distribute
2(3x)+2(-9)=18x
6x-18=18x
minus 6x both sides
-18=12x
divide both sides by 12
-18/12=x
-9/6=x
-3/2=x
easier way is to first divide both sides by 2
x=-3/2