Answer:
A = 0.16
Explanation:
Step 1) it is known that B^2 = A - therefore 8^2 = 64.
Step 2) since B in the question = 0.4 (see it as 4/10) - logically - you square the numerator and denominator to get (4^2/10^2) - then solve the exponents to get (16/100) or 0.16