find all sets of two consecutive positive odd integers whose sum is no greater than 18

So x + y <=18
y = x + 1

x + x + 1 <=18
2x + 1 <= 18

Subtract 1 from both sides
2x <= 17
x<=8.5 --> 8
So we have {(0,1),(1,2),(2,3),(3,4),(4,5),(5,6),(6,7),(7,8),(8,9)}