5.1/1.7+2.6*6 9.99/3.7/6 1.2*[0.8/(1-0.98)] 6/[11.1-(9.1-3)] 以上题目用简便计算怎么算?

5.1/1.7+2.6*6
=3+15.6
=18.6
9.99/3.7/6
=3*3*1.11/(3.7*6)
=9/6*1.11/3.7
=1.5*0.3
=0.45
1.2*[0.8/(1-0.98)]
=1.2*0.8/0.02
=1.2*40
=48
6/[11.1-(9.1-3)]
=6/(11.1-9.1+3)
=6/(2+3)
=1.2