We need to use the Phytagorean Theorem:

Where 'a' and 'b' are the legs of the right triangle, and 'c' is the hyptotenuse.
So it wants to know the hypotenuse, so that means that '10' and '3' are the legs of the right triangle and we can substitute those numbers for 'a' and 'b' and solve for c.
So, plugging in the values for 'a' and 'b' :

We can now expand what

and

equal to:

Now we add

and


So now we have to take the square root to get the value for 'c' or the hypotenuse:

And so the value of the hypotenuse will be

And if it wants the answer in decimal form, that would be:
