The question was: A bat and ball cost $1.10. The bat costs one dollar more than the ball. How much does the ball cost?
Answer: we are intuitively tempted to say 10c. But in that case, the total would be 10c + $1.10 = $1.20. (If the bat costs one dollar more than the ball, the bat must cost $1.10).
If the total cost is $1.10, then if the ball costs 10c, and the bat costs $1.00 then the bat costs only 90c more than the ball.
The correct answer is that the ball costs 5c (5c + $1.05 = $1.10).