Question 137341
How much gold is in 60g of 16k gold?  
{{{gold = 60*(16/24)}}} = {{{40g}}} 

Now set up an equation to solve for pure gold + 12k gold.

We know we have 60 grams total weight and 40g of gold.

Let X be the amount of pure gold in the mixture, then the amount of 12k gold is {{{60-X}}}

{{{gold Content = (Pure gold * X) + 12kGold*(60-X) }}}
{{{40 = (24/24) * X + (12/24)*(60-X) }}}
{{{ 40*24 = 24X + 720 - 12X }}}
{{{ 960 - 720 = 12X }}}
{{{ 240 = 12 X }}}
{{{ 20 = X }}}

So we need to mix 20g of pure gold with 40g of 12k gold to get 60g of 16k gold.

Check your answer
Does {{{40 = 20 + 40*(0.50)}}}???