How many litres of a $3\%$ hydrogen peroxide solution should be mixed with $6$ liters of a $30\%$ hydrogen peroxide solution so as to get a mixture of $12\%$ solution ?

Option (D)

Let x litres of hydrogen peroxide solution should be added, then

0.03x + (0.3)(6) = 0.12(x + 6)

$\implies 0.09x = 1.08 \implies x = 12$