Rebus
Explanation
The Joke
The comic is titled "Funtime Activity: Rebus Puzzles With No Proper Answer." A man holds up a sign showing a rebus puzzle consisting of a duck, a wrench, the letter T, and an ankle/foot. The woman says she gives up. The man indignantly tells her the answer is "duckwrenchtankle" and asks "What are you, stupid?" -- as if this obvious nonsense word should have been self-evident.
The Humor
The comedy comes from subverting the entire premise of rebus puzzles. In a normal rebus, pictures and symbols combine to form a recognizable word or phrase (for example, an eye + a can = "I can"). The puzzle shown here has no such clever solution -- the images just concatenate into the gibberish word "duckwrenchtankle." The man presenting it acts as though the answer is obvious and the woman is dumb for not getting it, which inverts the typical dynamic of rebus puzzles where the solver feels clever for decoding a hidden message. The joke is that when a rebus has no proper answer, the "solution" is just literally naming the pictures in order -- which is trivially easy and completely pointless, yet the man treats it as a test of intelligence.
References
A rebus is a puzzle in which words or phrases are represented by combinations of pictures, letters, and symbols. They have a long history dating back to ancient civilizations and remain popular as word games and brain teasers.