[tex]a \: \: b \: \: c \: - nr.[/tex]
[tex] \frac{a + b + c}{3} = 2.1[/tex]
[tex] \frac{a + b + c}{3} = \frac{21}{10} [/tex]
[tex]10(a + b + c) = 21 \times 3[/tex]
[tex]10a + 10b + 10c = 63[/tex]
[tex]a = 0.3[/tex]
[tex]b = 2.4[/tex]
[tex]10 \times 0.3 + 10 \times 2.4 + 10c = 63[/tex]
[tex]3 + 24 + 10c = 63[/tex]
[tex]27 + 10c = 63[/tex]
[tex]10c = 63 - 27[/tex]
[tex]10c = 36[/tex]
[tex]c = \frac{36}{10} [/tex]
[tex]c = 3.6[/tex]