You can put this solution on YOUR website! This is difference of 2 squares (36x^2 is 6x*6x) and 100 is 10*10.
Usually that would be enough to say = and call is a day. But in this case, you can see that each term includes a common factor of 2. = etc.
So
Alternatively, you might have seen that 36 and 100 are both products of 2 squares.
36 = 9*4
100 = 25*4
If you factor out the 4, you are still left with a difference of 2 squares
Which simplifies to the same result.
All this just confirms that in mathematics, there are many ways to get to the same answer (hopefully correct) answer.
Hope that helps