1 2 3 4 5 6 8 9 10 12
15 18 30 36 40 60 72 90
6的倍数
72的因数
6+3.4= 9.2-6= + = 1- - =
+ = - = 5- = + - + =
①+2-1÷7 ②-(-)
③-+-2.75 ④+++++