10x-5( 15-x)= 120

10x-75+5x= 120

15x= 195

x= 13

A: Xiaoyun answered the question 13.

Verification: 13X 10= 130 (correct score)

15- 13=2 (wrong question)

2X5= 10 (incorrect answer score)

130-10 =120 (final score)