Answer:
A is equal to 20.
Step-by-step explanation:
To find the missing side we have to square both 21 and 29.
Because 21 x 21 = 441, and 29 x 29 = 841, all we have to do is subtract 841 from 441 and we have 400.
Now we have to find the square root of 400, since 20 x 20 = 400, that means 20 is our answer.
