Is 49 a perfect square yes or no

Yes

(this is me just adding characters so that it accepts it)

The side x is the hypotenuse of the triangle.

And we know that the leg that is labeled with a line is also 6.

Use the Pythagorean theorem and solve for x.

a² + b² = x²
3² + 6² = x²
9 + 36 = x²
45 = x²
√45 = x
√9×5 = x
√9√5 = x
3√5 = x

The answer is 3√5

Hope this helps :)