(2+5)÷2=3.5 (2+5+5)÷3=4 (2+5*n)÷(1+n)=4.9 n等于多少

问题描述:

(2+5)÷2=3.5 (2+5+5)÷3=4 (2+5*n)÷(1+n)=4.9 n等于多少