When memrise asks you to type an answer that starts with a number, it will accept the answer if you only type the number.
For example, in http://www.memrise.com/course/116195/advanced-food-and-restaurant-menu-guide you learn the word 地三鲜, which translates to “3 fresh ingredients (potato, eggplant, green peppers)”. When asked to translate this, you can simply type “3” and then the answer will be accepted.
Am I the only one who noticed this? It’s a pretty old bug.