The eternal battle between people who remember PEMDAS and those who just... don't. The equation 230 - 220 * 0.5 equals 120 if you ignore order of operations (230 - 110 = 120), but it's actually 120 if you follow the rules (220 * 0.5 = 110, then 230 - 110 = 120).
Wait... both answers are 120? That can't be right. Let me recalculate... Oh, it's actually 230 - 110 = 120! The meme is claiming the answer is 5, which is spectacularly wrong, hence the normal distribution of intelligence showing most people getting it correct while the extremes (both geniuses and, well, not-so-geniuses) somehow agree on the wrong answer.
This is basically Facebook comment sections whenever someone posts "Only geniuses can solve 2+2×2!" and then everyone fights to the death about whether it's 6 or 8.