Can anybody explain how this was even the solution to the math problem

Okay so I'm learning how to solve a problem from my math text and they show the steps on how to solve it, but already and I'm getting stuck at Step 3. The problem was at first, from Step 2, "9 - (x^2)/4" and then all of a sudden it just goes from that to "(36 - x^2)/4". So my question is, how do you get from the number "9" to "36"? Wouldn't the next step be more like "(9 - x^2)/4" than "(36 - x^2)/4"? That was the really confusing part. And can you explain how they got from Step 3 to the Solution? I know you're supposed to square-root both sides of the equation to get the "h^2" to be unsquared. But when I square-rooted both sides, my Solution to the problem ended being "h = [sq.rt(36 - x^2)]/2? Please help.

Problem: h^2 + (x/2)^2 = 3^2
Step 1: h^2 = 3^2 - (x/2)^2
Step 2: h^2 = 9 - (x^2)/4
Step 3: h^2 = (36 - x^2)/4
Solution: h = 1/2 sq.rt(36 - x^2)

Step 2: h^2 = 9 - (x^2)/4

.9........(x^2)
***..-..*******
.............4

.9........(x^2)
***..-..*******.............common denominator is 4
.1...........4

.9*4.......(x^2)
*****..-..*******
.1*4..........4

.36.........(x^2)
*****..-..*******
..4............4

36.-.(x^2)
***********...........................… 3
......4


Step 3: h^2 = (36 - x^2)/4

.........36-x^2
h^2=********
............4

..................sqrt(36-x^2)
sqrt(h^2)=**************
.....................sqrt(4)

.....sqrt(36-x^2)
h=**************............OR
...............2


h = 1/2 sq.rt(36 - x^2)............SOLUTION STEP

Hope that was most helpful

The solution is supposed to be √36 - 4h^2
This is how I got it:
Problem: h^2 + (x/2)^2 = 3^2
Simplify all terms first.
h^2 + x^2 / 4 = 9
Isolate the x^2
x^2 = 4(9 - h^2)
Take the square root of both sides.
x = √36-4h^2

*Edit
My mistake, I didn't know the problem wanted to solve for H instead of X.
In that case
h = √(9 - x^2 /4)