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 mineral's hardness is a measure of its relative resistance to scratching, measured by scratching the mineral against another substance of known hardness on the Mohs Hardness Scale.