[1－(2/3+1/5)×1/13]＋7/10
=[1－(10/15+3/15)×1/13]＋7/10
=[1－13/15×1/13]＋7/10
=[1－1/15]＋7/10
=14/15+7/10
=28/30+21/30
=49/30
