问题补充：0.64×25×7.8+2.2
=0.16*4*25*7.8+2.2
=0.16*100*7.8+2.2
=16*7.8+2.2
=127
2÷2.5+2.5÷2
=4/5+5/4
=2.05
194－64.8÷1.8×0.9
=194-36*0.9
=194-32.4
=161.6
36.72÷4.25×9.9
=8.64*9.9
=85.536
5180－705×6
=5180-4230
=950
24÷2.4－2.5×0.8
=10-2
=8
(4121+2389)÷7
=6510/7
=930
671×15-974
=10065-974
=9091
469×12+1492
=5628+1492
=7120
405×(3213-3189)
=405*24
=9720