Okay so you need to use the Pythagorean theorem which is a^2 + b^2 = c^2
13^2 + b^2 = 47
169 + b^2 = 2,209
Move constant to the right
b^2 = 2,209 - 169
Subtract the numbers
b^2 = 2,040
Take the root of both sides
The final steps an answers are above on the image;)
