x∈ℕ
18/(x-3) => (x-3)|18 => x-3∈{1,2,3,6,9,18}
x∈{4,5,6,9,12,21}
1/(x+1) => (x+1)|1 => x+1∈{1} /-1
=> x=0
35/x => x|35 => x∈{1,5,7,35}
24/(12-x) => (12-x)|24 => 12-x∈{1,2,3,4,6,8,12,24}
x∈{0,4,6,8,9,10,11,12}
17/(2x-2) => (2x-2)|17 => 2x-2∈{1,17}
2x∈{3,19}
x∈{3/2;19/2}
dar: x∈ℕ => x∈Ø
