Problem 1. Grandfather Frost had 120 chocolate candies and 200 jelly candies. At the morning performance, he gave candies to the children: each child received one chocolate candy and one jelly candy. Counting the candies after the performance, Grandfather Frost found that there were three times as many jelly candies left as chocolate candies. How many children were at the performance?
Answer: 80.

Solution. Let the total number of children be $x$, then after the morning party, Grandfather Frost had $120-x$ chocolate candies and $200-x$ jelly candies left. Since there were three times as many jelly candies left as chocolate candies, we get the equation $3 \cdot(120-x)=200-x$. Solving this, we get $x=80$.

## Criteria

One of the largest suitable criteria is used:

## 7 points. Any complete solution of the problem.

2 6. The correct answer is given with a check that it fits, but it is not proven that there are no other answers.