To expand upon the previous (completely correct) reply, you would use the exact same steps as you've always used (such as when you were,
in another thread, finding the inverse of a matrix). The only difference is that you won't be able to simplify as much, between steps, due to the variable.
You have:
[ 0 2 2 ]
[ 1 h 0 ]
[-2 7 h ]
A good start would probably be to multiply the second row by 2, and add this to the third row, creating a new third row:
2*R2 + R3 -> R3
[ 0 2 2 ]
[ 1 h 0 ]
[ 0 7+2h h ]
Obviously, dividing the first row through by 2 would be helpful!
(1/2)R1 -> R1
[ 0 1 1 ]
[ 1 h 0 ]
[ 0 7+2h h ]
Then try multiplying the first row by -(7 + 2h), and adding the result to the third row. Also, multiply the first row by -h, and adding the result to the second row. Once you simplify, you can reorder the rows, and you should have your answer.