a: x+2/5=1/2
nên x=1/2-2/5=5/10-4/10=1/10
b: x+3/7=2/5+3/10
=>x+3/7=4/10+3/10=7/10
=>x=7/10-3/7=49/70-30/70=19/70
c: 2/3-x=8/21
=>x=2/3-8/21=14/21-8/21=6/21=2/7
d: 19/20-x=8/5-3/4
=>19/20-x=32/20-15/20=17/20
=>x=2/20=1/10
BT1
a)x+2/5=1/2 b)x+3/7=2/5+3/10 c)2/3-x=8/21 d)19/20-x=8/5-3/4
x=1/2+2/5 x+3/7=7/10 x= 2/3-8/21 19/20-x=17/20
x=9/10=0.9 x=19/70 x=2/7 x=1/10=0,1
a: x+2/5=1/2
nên x=1/2-2/5=5/10-4/10=1/10
b: x+3/7=2/5+3/10
=>x+3/7=4/10+3/10=7/10
=>x=7/10-3/7=49/70-30/70=19/70
c: 2/3-x=8/21
=>x=2/3-8/21=14/21-8/21=6/21=2/7
d: 19/20-x=8/5-3/4
