The answer is multiply the numbers and add odd number sequence.
For example: The product (y x z = x) is x. The odd numbers sequence is 1, 3, 5, 7, 9 etc. is added to the product. Add x + odd number sequence.
3 x 2 = 6 + 1 = 7
5 x 4 = 20 + 3 = 23
7 x 6 = 42 + 5 = 47
9 x 8 = 72 + 7 = 79
10 x 9 = 90 + 9 = 99
The answer is 99.