Carly tutors students in math on the weekends and offers both thirty-minute sessions and sixty-minute sessions. She earns $15 for each thirty-minute session and $25 for each sixty-minute session.

If she earned $230 this past weekend and had x thirty-minute sessions and x - 2 sixty-minute sessions, what is the value of x?

A. 7
B. 8
C. 5
D. 6