Answer: 12 grams
Step-by-step explanation:
To find 10% of a number, you can multiply the number by 0.1.
In this case, the total mass of the coin is given as 120 g.
To find the mass of the gold, we can multiply 120 g by 0.1:
120 g * 0.1 = 12 g
Therefore, the mass of the gold in the coin is 12 grams.