Find the length of the missing side. If necessary, round to the nearest tenth.

Answer:
17.32 units
Step-by-step explanation:
The above triangle is a right-angled triangle understood by the small square which denotes the angle there is 90°
Using Pythagoras theorem for right-angled triangle,
b^2+10^2=20^2
or,b^2+100=400
or,b^2=300
or,b=10√3=17.32 units. [ANS]