Answer: Damien has 21 red pieces
Explanation:
First, 7/8 of the rectangle is coloured red.
Then, the 7/8 was cut into a size 1/24 of the rectangle each.
That consequently means that 24 of those pieces will form the whole shape.
Since red covers 7/8 of the rectangle, the number of red pieces invariably becomes
⅞ × 24 pieces, which is equal to 21 pieces
Therefore, Damien has cut the red part of the rectangle into 21 pieces