1. The sum of positive integers is 11. In the first part of this equation, identical numbers are hidden behind cards with the same letters, and different numbers - behind cards with different letters.

Consider the equation: $\quad \mathbf{C}+\mathbf{y}+\mathbf{M}+\mathbf{M}+\mathbf{A}=11$.

Can you tell which number is hidden behind the letter M?
Answer: 1. Solution. If $M=1$, then the sum $C+y+A=9$, which is only possible with the set of numbers 2, 3, 4 (in any order). If $M=2$, then the sum $C+y+A=7$, which is impossible, as this sum is not less than $1+3+4=8$. If $M>2$, this is even more impossible.