[Algebra]
Problem: Given that April $1^{\text {st }}, 2012$ fell on a Sunday, what is the next year in which April $1^{\text {st }}$ will fall on a Sunday?

Solution: Note that $365=7 \cdot 52+1$. Thus over the next few years after 2012 , the day of the week for April $1^{\text {st }}$ will advance by one day in a non-leap year, and it will advance by two days in a leap year. Thus in six years, the day of the week will have rotated a complete cycle, and the answer is 2018 .

Final answer: 2018