For every apple you have one more orange. You could divide 12 by 3 an you would get 4. so you add 4 more to 12 and you get 16 oranges. Or you could just multiply 4 by 4.
You can multiply by 12 because to get rid of the fractions all terms should be divided by the LCM (ie the smallest multiple that is exactly divisible by 2, 4 and 3)
Multiples of 3 = 3, 6, 9, 12
Multiples of 4 = 4, 8, 12, 16
Multiples of 2 = 2, 4, 6, 8, 10, 12
Therefore the fractions should be multiplied by 12
