Bài 1:
a) $A=(456.11+912).37:13:74$
$A=(5016+912).37:13:74$
$A=5928.37:13:74$
$A=219336:13:74$
$A=16872:74=228$
b) $B=[(315+372).3+(372+315).7]:(26.13+74.14)$
$B=[(315+372).(3+7)]:(338+1036)$
$B=[687.10]:1374$
$B=6870:1374=5$
Lưu ý: Dấu "." là dấu nhân
Bài 2:
a) $70-5.(x-3)=45$
$5.(x-3)=70-45=25$
$x-3=25:5=5$
$⇒x=5+3=8$
b) $12+(5+x)=20$
$5+x=20-12=8$
$⇒x=8-5=3$
c) $14.x+54=82$
$14.x=82-54=28$
$⇒x=28:12=2$
d) $130-(100+x)=25$
$100+x=130-25=105$
$⇒x=105-100=5$
