Câu `1:`
`2xx4xx8xx50xx25xx125`
`=8xx400xx3125`
`=3200xx3125`
`=10000000`
Câu `2` :
$1050m/p=37800km/h$
Vì `1050xx3600:100=37800`
Câu `3` :
`(A+A)/(AxxA)=1/2`
`=>2.2A=A.A`
`=>A.A-4A=0`
`=>Axx(A-4)=0`
`=>A=4`
Câu `4` :
`0,75%=0,0075=75/10000`
Câu `5:`
`(x+1)+(x+3)+(x+5)+...+(x+27)=224`
`=>(x+x+x+...+x)+(1+3+5+...+27)=224` ( Có `(27-1):2+1=14` số `x` )
`=>(x+x+x+...+x)+((27+1)xx14:2)=224`
`=>14 xx x+196=224`
`=>14xx x=224-196`
`=>14xx x=28`
`=>x=28:14`
`=>x=2`
