I think the first problem you posted is solved incorrectly.
1.
sq root of 125 = square root of (25 x 5)
sq root of 125 = 5 x sq root of 5

2.
sq root of 75 = sq root of (25 x 3)
sq root of 75 = 5 x sq root of 3

Hope this helps

if you need to simplify the square roots, try to do so by dividing them into prime factors.

Hence,

sqrt 125 :sqrt 5
sqrt 25 :sqrt 5
dqrt. 5 :sqrt 5

thus, Square Root of 125= (Sqrt 5 X Sqrt 5) X (Sqrt 5)

I only put the paranthesis to make you see it easier that Sqrt 5 X Sqrt5=5

The result of the simplification would therefore be 5sqrt5

Thank you all .. I understood how to simplify square roots

I appreciate your help!