①36+61.2÷12
=36+61.2÷12
=36+5.1
=41.1
②（20-1.4÷2）×0.4
=（20-0.7）×0.4
=19.3×0.4
=7.72
③54÷（3.94+6.86）×0.8
=54÷10.8×0.8
=5×0.8
=4