表达存钱与合理消费 — 英语填空题
题目
Tom gets 60 yuan of pocket money every week. He wants to buy a schoolbag for 90 yuan. He tells his mum, "I won't spend all my money. I will save half of it every week and spend the rest on things I need." If he starts this week, he needs to save for ___ weeks to have enough money for the schoolbag.