7/13-3/7+7/13-2/7
=7/13+7/13-(3/7+2/7)
=14/13-5/7
=1又7/91-65/91
=33/91
14/13-5/7=3/91
7/13加上7/13得到14/13,
3/7加上2/7得到,5/7,等价于10/14,
14/13减去10/14
等价于(14✘13)/(14✘13)减去(10✘13)/(14✘13),得到(4✘13)/(14✘13),
得到2/7
7/13-3/7+7/13-2/7
=(7+7)/13-(2/7+3/7)
=14/13-5/7
=1/13+2/7=0.362637
7/13-3/7+7/13-2/7
=(7/13+7/13)-(3/7+2/7)
=14/13-5/7
=98/91-65/91
=33/91
运用加法交换律、结合律,通分,计算。