option 1
Quantity of gold in 1 kg of alloy
‘A’ =$\frac{7}{29}$
Quantity of gold in 1kg of alloy ‘B’=$\frac{21}{58}$
Quantity of gold in 1 kg of alloy
‘C’ =$\frac{25}{87}$
Required ratio= ($\frac{21}{58}$-$\frac{25}{87}$):($\frac{25}{87}$-$\frac{7}{29}$)
13 : 8