Răspuns:
a= 18, b=45, c=63
Explicație pas cu pas:
[tex]\frac{a}{2} =\frac{b}{5} =\frac{c}{7} \\5a= 2b\\7a=2c\\b=\frac{5a}{2} \\c=\frac{7a}{2} \\3a+ 2*\frac{5a}{2} - \frac{7a}{2} = 81\\3a+ \frac{10a}{2} - \frac{7a}{2} = 81\\\frac{6a+10a-7a}{2} =81\\9a=162\\a= 18\\b=\frac{5a}{2} \\b= 45\\c=\frac{7a}{2} \\c= 63\\[/tex]
