Total number of pens -> 100u

Since green pens was ¼ of blue and red combined,

Green pen -> 1p

Blue + Red -> 4p

1p + 4p = 100u

1p = 20u

Green pen -> 20u or 20%

Blue pen -> 32u or 32% (given)

Red pen -> 100u – 20u – 32u = 48u

(a) Percentage of red pens -> 48%

(b) Blue : Green : Red = 32 : 20 : 48 = 8 : 5 : 12

50% of blue pen -> 32u × 50% = 16u

16u = 8

1u = 0.5

(c) Number of red pens -> 48 × 0.5 = 24