Answer: 12.32 is the answer.
Step-by-step explanation: Using the pythagorean thereom we can solve this by using the formula A^2+B^2=C^2.
We substitute in the values,
17^2+B^2=21^2.
Now we simplify.
289+B^2=441
We subtract the 289 from both sides,
B^2=152
Now we use square root to find the answer.
12.32 is the answer.
Hope this helps!
