Question

the product of two numbers is 18 if one number is 8by2/5 find the other number

Answer 1

Assuming that by 8by2/5 you mean (8/2)/5, that equals 8/(2*5) which in turn equals 4/5. Now to get the other number, divide 18 by 4/5 which equals (18*5)/4 or 22.5.