31. My brother didn't play tennis yesterday. He was playing tennis the day before yesterday.
В первой части предложения необходимо использовать Past Simple в отрицательной форме, так как действие не произошло вчера (yesterday). Во второй части необходимо использовать Past Continuous, так как действие происходило в определенное время в прошлом (the day before yesterday).
Ответ: My brother didn't play tennis yesterday. He was playing tennis the day before yesterday.