Giải thích các bước giải:
$a)53.39+47.39-53.21-47.21$
$=53(39-21)+47(39-21)$
$=53.18+47.18$
$=(53+47).18 $
$=100.18$
$=1800$
$b)2.53.12+4.6.87-3.8.40$
$=2.12.53+24.87-24.40$
$=24.53+24.87-24.40$
$=24.(53+87-40)$
$=24.100$
$=2400$
$c)5.7.77-7.60+49.25-15.42$
$=35.77-7.5.12+7.7.5.5-3.5.7.6$
$=35.77-35.12+35.35-35.18$
$=35.(77-12+35-18)$
$=35.82$
$=2870$
Học tốt!!!