In a math contest, I did ten questions, one of which was right and the other was wrong, and five points were deducted.
Xiaohua took part in the math contest, * * * 10. It is stipulated that the correct answer is given ten points, and the wrong answer is deducted five points. Xiaohua answered all ten questions and got 85 points. How many questions did Xiaohua answer correctly?
10-( 10× 10-85)÷( 10+5)
= 10-( 100-85)÷ 15
= 10- 15÷ 15
= 10- 1
=9 (question)