简便计算.5.68减4.98减0.11,1除以（1减0.98）,9.9乘7.8.

5.68-4.98-0.11=5.68-5+0.02-0.11=0.68+0.02-0.11=0.59
1/(1-0.98)=100/(100-98)=50
9.9*7.8=(10-0.1)*7.8=10*7.8-0.1*7.8=77.22

5.68-4.98-0.11
=0.7-0.11
=0.59
1÷（1-0.98）
=1÷0.02
=（1x5）÷（0.02x5）
=5÷0.1
=50
9.9x7.8
=（10-0.1）x7.8
=10x7.8-0.1x7.8
=78-0.78
=77.22