Answer:
5.3
Explanation:
You use the Pythagoras theorem which is a^2+b^2=c^2.
Since you're solving for a side length that's not the hypotenuse you will manipulate the equation to c^2-a^2=b^2. From here you just plug in numbers.
8^2 - 6^2 = b^2
64 - 36 = b^2
b = sqrt(28)
b = 5.2915.... = 5.3