[OFFICIAL] Basic Math/Combinatorics Problems

can u please explain 2 c)

also 1 b) (i got the same answer just want to know approach)

my 1b) -

(n+1 ‘R’) (1 ‘L’) (m ‘U’) but ‘L’ cant come first or last - so only n/(n+2) cases valid

    (n + m + 2)!               n
    ------------     *       -----
    (n + 1)!   m!           (n + 2)