Question

what is the next number

Answer 1

4 × 7 - 1 = 27
5 × 8 - 2 = 38
6 × 9 - 3 = 51

Answer 2

you can see this:
4 * 7 - 1 = 27
5 * 8 - 2 = 38
6 * 9 - 3 = 51