Let's write the equation properly:
[tex] \cfrac{10}{8+h} = \cfrac{9}{3}-2 [/tex]
The right hand side can be simplified a lot: 9/3=3, so we have 3-2=1. The equation can be written as
[tex] \cfrac{10}{8+h} = 1 [/tex]
We can multiply both sides by the denominator to get
[tex] 10 = 8+h [/tex]
At this point, you simply have to subtract 8 from both sides to get
[tex] h = 2 [/tex]
