7/10x99+7/10
=7/10x(99+1)
=7/10x100
=70
34÷35×36
=1224/35
98×96/97
＝(1+97)x96/97
=96/97+96
=96又96/97
42×（19/14-8/21）
=42x（57/42-16/42）
=42x41/42
=41