If any one out there knows how to do this please tell me

Answer: 17.32 or 17
Step-by-step explanation:
Using Pythagoras theorem
20^2=10^2+b^2
20^2 - 10^2=b^2
300=b^2
Taking square root on both sides
√300=b
b=17.32
Answer:
17.32
Step-by-step explanation:
x² + 10² = 20²
x² + 100 = 400
x² = 400 - 100
x² = 300
x = √300
x = 17.32