first aline the decmials like you would regularly do to multiply.
Then multiply 2 x 6=12 and then 2 x 3=6 and put them down were you would already do noramly multiplying.
and then muliply 4x6=24 and 4x3=12 and do the same thing as you would do normaly and then add 72 and 144 to get 1512 and then count your decmail placing. which is 2 placeing in total which makes 1512 into 15.12