Question

(Problem on image.)...

Answer 1

Hey there! :) 

In order to the find the missing side length of this triangle, we'll need to use the Pythagorean Theorem! 

That equation is : a² + b² = c²

a = adjacent side

b = long side of rectangle

c = hypotenuse

We're already given the values of both a & c, so let's plug everything in! 

a² + b² = c²  → a = 10 , b = ? , c = 20

(10²) + b² = (20²)

Simplify.

100 + b² = 400

Subtract 100 from both sides.

b² = 400 - 100

Simplify.

b² = 300

Get the square root of b² & 300.

$\sqrt{b^2} = \sqrt{300}$

Simplify!

b = 17.3

So, the missing side length is the first answer choice : 17.3

~Hope I helped!~