To find Tom's score, we can set up the equation based on the information given:
\[ 20 + \text{Tom's score} = 73 \]
Now, let's isolate Tom's score by subtracting 20 from both sides of the equation:
\[ \text{Tom's score} = 73 - 20 \]
Calculating the right side:
\[ \text{Tom's score} = 53 \]
So, Tom's score is 53.