On dividing the given number by 342,let k be the quotient and 47 as remainder.
Then, number `=342k+47`
                     `=(19x18k+19x2+9)=19(18k+2)+9`
      `:.`The given number when divided by 19,gives (18k+2) as quotient and 9 as remainder.

(i) Let`x/147`=29.Then,`x = (147 xx 29) = 4263.`
  
 :.Missing number is 4263.

 (ii) Let`xx 144 =12528.`Then,x=`12528/144`=87.

The required numbers are `14,21,28,35....77,84.`
This is an A.P. with `a=14` and `d=(21-14)=7`.
Let it contain n terms.
Then,`T~n=84`
`⇒ a+(n-1)d=84`
`⇒ 14+(n-1) xx 7`
`=84 or n=11`
`:.` Required number of terms `=11`

The given numbers are `1,3,5,7.....99,`
This an A.P with a=1 and d =2.
Let it contain n terms.Then,
`1+(n-1) xx 2=99 or n=50.`
`:.`Required sum =`n/2 ("first terms" + "last terms")`
                       =`50/2 xx (1+99)=2500`.

All 2 digit numbers divisible by `3` are :

 `12,15,18,21,......99`.

 This is an A.P. with `a =12` and `d=3`.

 Let it contain n terms.Then,

 `12+(n-1) xx 3=99` or `n=30`.

 Required sum =`30/2 xx (12+99) = 1665`.