(a) Concept: 1 Mark
      Solution: 1 Mark
(b) Solution: 1 Mark
(c) Solution: 1 Mark
(a) Total no of balloons = 55
Balloons left with Nisha = 55 - 46 = 9
Fraction of balloon left = $\frac{9}{55}$
Balloons left with Nisha = 46 - 6 = 40
Fraction of balloon left with Nisha = $\frac{40}{46}=\frac{20}{23}$
(b)The total weight of the fruits = $3\frac{1}{2}+4\frac{3}{4}$
= $\frac{7}{2}+\frac{19}{4}$
=  $\frac{14}{4}+\frac{19}{4}$
=  $\frac{33}{4}$
=  $8\frac{1}{4}$
(c) $2\frac{2}{3}+3\frac{1}{2}=\frac{8}{3}+\frac{7}{2}$
                         $=\frac{8\times 2+7\times 3}{6}$
                        $=\frac{16+21}{6}$
                        $=\frac{37}{6}$
                       $=6\frac{1}{6}$