<span>The answer is that 79 IS NOT correct because the riddle says "my ones digit is 2 LESS than my tens digit.." and 79 has 7 in tens and 9 in ones.</span>
The distance of A from the origin.
√(5²+3²+(-2)²)= √(25+9+4)
=√38
=6.2
The distance of B from the origin
√(2²+(-4)²+8²=√(4+16+64)
=√84
= 9.2