Đáp án:
Giải thích các bước giải:
`5-(x/12 +1/4 + {60-x}/15 )=1/2` MTC: 60
`=>`` 5-(5x/60 +15/60 + {4(60-x)}/60 )=1/2`
`=>` `- ({5x+15+4(60-x)}/60 ) =1/2`
`=>` `5-( {255+x}/60 )=1/2`
`=>``5-( {255+x}/60 )-1/2=0`
`=>`` 9/2-( {255+x}/60 )=0`
`=>` `270/60-( {255+x}/60 )=0`
`=>` `{270-255-x}/60 =0`
`=> {15-x}/60 =0`
`=>15-x=0`
`=>x=15`