a) `100≤x≤(1+3+5+7+...+199)`
`⇒ 100≤x≤((199+1).100)/2`
`⇒ 100≤x≤10000`
`⇒ x={100; 101; 102;...; 9999; 10000}`
b) `1 / (1/4)`+`5/6`≤`x/36`≤`3/(1/2)`+`4/(1/9)`
`⇒ 29/6 ≤ x/36 ≤ 42`
`⇒ 174/36 ≤ x/36 ≤ 1512/36`
`⇒ 174 ≤ x ≤ 1512`
`⇒ x = { 174; 175; ...; 1512}`