Hoi!
Since the unknown side of the triangle is equal to the known side of the rectangle (6), then the value of the unknown side is 6. Now that we have two side lengths for the triangle, we use the Pythagorean Theorem to find the value of the hypotenuse.
Pythagorean Theorem: a² + b² = c²
Plug in the values
6² + 3² = x²
36 + 9 = x²
45 = x²
Now we just take the square root of x
√45 = 6.7
Let's look at our answer choices, and figure out which one matches.
A obviously doesn't match
B: √3 × 3 = 5.1 - Close, but it's still not 6.7
C: √5 × 3 = 6.7
C is your answer
