Ответ: Did she teach science on Friday? No, she didn't. She taught maths.
Составляем вопрос, используя вспомогательный глагол Did для прошедшего времени (Past Simple) и информацию из условия: teach science / on Friday.
Did she teach science on Friday?
Отвечаем отрицательно, используя no/maths из условия. Составляем отрицательный ответ: No, she didn't. She taught maths.
Ответ: Did she teach science on Friday? No, she didn't. She taught maths.