Nice linear equation problem. The key concept being tested is translating "X percent/fraction longer" correctly — a very common source of errors in Problem Solving.
Step 1 — Translate "3/4 longer" into math.
"The drama is 3/4 longer than each of the other two films" means:
Drama = shorter film + (3/4) × shorter film = (1 + 3/4) × shorter film = (7/4) × shorter film
This is NOT the same as drama = (3/4) × shorter film. "3/4 longer" means you ADD 3/4 of the base, giving a multiplier of 7/4.
Step 2 — Set up variables.
Let the comedy = documentary = x minutes (the two shorter films have the same length).
Drama = (7/4)x minutes.
Step 3 — Account for all time.
Total time = drama + comedy + documentary + 2 breaks
400 = (7/4)x + x + x + 2(20)
400 = (7/4)x + 2x + 40
360 = (7/4)x + 2x
360 = (7/4)x + (8/4)x
360 = (15/4)x
x = 360 × (4/15) = 96 minutes
Step 4 — Answer the question asked.
The documentary = x = 96 minutes.
Answer: C (96 minutes)
Common trap: Many students read "3/4 longer" and compute drama = (3/4)x instead of (7/4)x. If you make this mistake, you get (3/4)x + x + x + 40 = 400, which gives x = 128 — not one of the answer choices, which should signal an error in your setup.
A second trap: the question asks for the documentary specifically, but since comedy = documentary = x, this doesn't change the final answer here. Still, always re-read what is being asked before writing down your answer.
Takeaway: Whenever you see "A is [fraction] longer than B," always write A = (1 + fraction) × B, never A = fraction × B.