If M=number of matinee tickets, E= number of evening tickets:
M+E=378 so E=378-M (ticket totals)
6.5M+8.75E=2929.50 (ticket sales)
6.5M+8.75(378-M)=2929.50
6.5M+3307.50-8.75M=2929.50
378=2.25M so M=378/2.25=168, and E=378-168=210.
168 matinee and 210 evening tickets were sold.