Answer:
It is Number 1 A
Step-by-step explanation:
The midpoint between these two would be -7, as you would add these two numbers, and then divide by two.
The missing numbers would be 12-6
Answer: 6 students
What we know:
Students: 24
Students who play checkers: 
Students who also play sudoku:
of the 
24 ÷ 3 = 8, so 8 × 2 = 16 (students who play checkers)
× 2 = 
So the answer is,
6 students play both checkers and sudoku