Find the pair of numbers that would fit into the pattern:
15 28, 17 25, 19 22, 21 19, ?

The series can be split into two separate alternating number tracks:
1. First numbers in each pair: $15,17,19,21,\dots$ (pattern is adding $+2$)

$$\text{Next first number}=21+2=23$$

2. Second numbers in each pair: $28,25,22,19,\dots$ (pattern is subtracting $-3$)

$$\text{Next second number}=19-3=16$$

Thus, the next pair in the sequence is 23 16.