B21: a, `28=14+14`
b, `28=20+8`
B22:
`1122= 33.34`
`2450=49.50`
`10302=101.102`
B23:
`576+429 = 429+276 + 300 = 729 +276 `
`-> 576 +429=729+276`
B24:
`200.200 = 200.199 + 200 > 200.199 + 199 =199.201`
`-> 200.200>199.201`
B25:
Có `a+5=b+7` ⇔ `a=b+2` ⇔ `a>b`
`b+7=c+10` ⇔ `b=c+3` ⇔ `b>c`
⇔ `a>b>c`
B26:
`98.102 = 98.100 + 2.98 < 100.98 + 2.100 =100.100`
`-> 98.102<100.100`
B27:
`2011.2013 = 2011.2012+2011 < 2011.2012 + 2012 = 2012.2012`
`-> 2011.2013 < 2012.2012`
