Question

2/5+1/2×3/5+7/10；12/13×3/7+4/7 用简便方法计算

Answer 1

2/5+1/2×3/5+7/10
=2/5+3/10+7/10
=2/5+1
=7/5
12/13×3/7+4/7
=(9/13+1)×4/7
=22/13×4/7
=88/91