imc

Each day, the cat eats $\frac{1}{3}+\frac{1}{4}=\frac{7}{12}$ of a can of cat food. Therefore, the cat food will last for $\frac{6}{\frac{7}{12}}=\frac{72}{7}$ days, which is greater than $10$ days but less than $11$ days. Because the number of days is greater than 10 and less than 11, the cat will finish eating in on the 11th day, which is equal to $10$ days after Monday, or $\boxed{\text{Thursday}}$