Answer:
Step-by-step explanation:
We see that this is a rectangle triangle, and that the ZY side is the hypotenuse.
It's length is then square root of the sum of the squares of the other sides:
So, in this case:
The 8 and 3 numbers are easy to get from the graphic... and the order doesn't matter (8² + 3² = 3² + 8²).
That's an easy rule to remember.
I hope it helps.