1. (7 points) 45 candies cost as many rubles as can be bought for 20 rubles. How many candies can be bought for 50 rubles?

Answer: 75 candies.
Solution. Let $x$ be the cost of one candy in rubles. Then $45 x=\frac{20}{x}$, from which $x=\frac{2}{3}$. Then with 50 rubles, one can buy $\frac{50}{x}=75$ candies.

Criteria. Any correct solution: 7 points.

The equation $45 x=\frac{20}{x}$ is correctly set up, but an arithmetic error is made in solving it or in subsequent steps: 5 points.

In the solution, it is claimed that the price of one candy is $\frac{2}{3}$, it is verified that this price fits the condition of the problem, and the correct answer is obtained: 4 points.

Only the correct answer is provided: 1 point.