The numbers are 9 and 2.
One number is 1 more than 4 times another.
2 x 4 = 8
8 + 1 = 9
Their product is 18.
9 x 2 = 18
Usually, with this type of problem, it's easiest just to use trial and error. Go through the factors of 18, and eventually you'll find a pair that fits the given criteria.