有一群小鸟，先飞走7只，又飞走6只，两次一共飞走多少只？'k;M;y+S
算式：提示3c'Q6g;p'?8v:J'A'x5c7N0|*R)r'k;M;y+S
答：两次一共飞走1J(i.o;?7x4`3S9|'Y.}3|7]只。'k;M;y+S