Asked to simplify 3x + 2y, Karan writes 5xy

Why

Karan has taken the 3 and the 2, added them to make 5, and stuck the letters together — treating x and y as if they were the same thing. You can only add terms that count the SAME kind of item. 3x means three x's and 2y means two y's, and just as three apples and two oranges do not make five apple-oranges, three x's and two y's do not make five xy's; they stay as separate terms. Test with numbers: let x be 1 and y be 1, then 3x + 2y is 3 + 2, which is 5, and 5xy is 5 times 1 times 1, also 5 — a match by luck; now let x be 2 and y be 1, and 3x + 2y is 6 + 2, which is 8, while 5xy is 5 times 2 times 1, which is 10, so the two are not equal. Nita is right, 3x + 2y stays as it is: only like terms, ones with exactly the same letters, can be added together.