Final answer:
After earning $50 and paying back the $10 he owed his sister, Tom has $40 remaining. The integer representing Tom's current amount of money is $40.
Step-by-step explanation:
The question asks which integer represents the number of dollars Tom has after earning money and paying his sister back.
Tom initially owed his sister $10. After earning $50 for mowing lawns, he paid her back the $10 he owed. To find the integer representing the money Tom has now, we need to subtract the money he owed from the money he earned:
$50 (earned) - $10 (owed) = $40
Therefore, the integer that represents the amount of money Tom has after paying his sister is $40.