1. Variant 1.

Currently, the mother is 24 years and 3 months old, and her daughter is 5 months old. After how many months will the number of years in the mother's age be equal to the number of months in the daughter's age?
Answer: 21.

Solution. Let $x$ be the required number of months. Then we get the equation: $24+(x+3) / 12=x+5$. From this, $x=21$.