Let x g and y g be the weight of 18-carat and 12- carat gold respectively.
As per the given condition
18x/24 + 12y/24 = 120 ×16/ 24
⇒3x + 2y = 320 …………(i)
And x + y = 120 …………(ii)
Multiplying (ii) by 2 and subtracting from (i), we get
x = 320 – 240 = 80
Now, putting x = 80 in (ii), we have
80 + y = 120
⇒ y = 40
Hence, the required weight of 18-carat and 12-carat gold bars are 80 g and 40 g respectively