Question

I need to check if I am heading to the right way.

Answer 1

Answer:

$12\sqrt[]{2}$

Explanation:

The sketch of the situation is given below

We need to find length B.

Now Pythagoras's theorem gives

$B^2+(4\sqrt[]{7})^2=20^2$

which simplifies to

$B^2+112=400$

subtracting 112 from both sides gives

$B^2=400-112$$B^2=288$

Taking the square root of both sides gives

$B=\sqrt[]{288}$

$\boxed{B=12\sqrt[]{2}\text{.}}$

which is our answer!