答案:1、买40分邮票张数为:(80x20-10x100)÷(80-40)=(1600-1000)÷40=600÷40=15张2、雨天为:(112÷14x20-112)÷(20-12)=(160-112)÷8=48÷8=6天3、打碎的瓶子为:(1000x0.3-260)÷(0.3+0.5)=(300-260)÷0.8=40÷0.8=50只4、蜘蛛有:17-(17x8-108)÷(8-6)=17-28÷2=17-14=3只蜻蜓和蝉共有:17-3=14只蝉有:(14x2-24)÷(2-1)=4÷1=4只蜻蜓有:14-4=10只