Răspuns :
[tex]a = mama \\ b = tata \\ c = copilul \\ a + b + c = 85 \\ b = a + 4 \\ c = a \div 4 \\ a + a + 4 + a \div 4 = 85 \\ a + a +4 + \frac{a}{4} = 85 \\ \frac{9}{4} a + 4 = 85 \\ 9a + 16 = 340 \\ 9a = 340 - 16 \\ 9a = 324 \\ a = 324 \div 9 \\ a = 36 \\ \\ a = 36 \\ b = 36 + 4 = 40 \\ c = 36 \div 4 = 9[/tex]