[tex] \frac{a+b+c}{3} =2,5 =\ \textgreater \ a+b+c=2,5*3=\ \textgreater \ a+b+c=7,5\\ a=b+0,7 =\ \textgreater \ a=2c+0,7\\ b=2c \\ 2c+0,7+2c+c=7,5 \\ 5c=7,5-0,7=\ \textgreater \ c=6,8:5=\ \textgreater \ c=1,36 \\ b=1,36*2=\ \textgreater \ b=2,72 \\ a=2,72+0,7=\ \textgreater \ a=3,42
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