To find out how much Dominic earned, we can start by letting the amount Brayden earned be represented as \( 3x \) and the amount Dominic earned as \( x \) since their earnings are in a ratio of 3:1.
According to the problem, the total earnings of both Brayden and Dominic is $48. Therefore, we can set up the equation:
\[ 3x + x = 48 \]
This simplifies to:
\[ 4x = 48 \]
Next, we solve for \( x \):
\[ x = \frac{48}{4} = 12 \]
Now, since \( x \) represents the amount Dominic earned, we find that Dominic earned $12.
Thus, the answer is $12.