(3分之1-7分之1)×21
问题描述:
(3分之1-7分之1)×21
答
(1/3-1/7)*21
=1/3 *21-1/7 *21
=7-3
=4
(3分之1-7分之1)×21
(1/3-1/7)*21
=1/3 *21-1/7 *21
=7-3
=4