What is 2/3h-1/3h+11=8? how do i do that?

2/3 h - 1/3 h + 11  =  8

You could begin by combining like terms on the left side.

Notice that you have (2 of something) minus (1 of the same thing).
The things are  (1/3 of 'h').  When you subtract the 1 from the 2,
what you have left there is 1/3h .

So now the equation is    1/3 h  + 11  =  8

Subtract  11  from each side :    1/3 h  =  -3

Multiply each side by  3 :    h  =  -9