Answer:
4
Step-by-step explanation:
To find the number you have to reverse the equation
Let us call the number "x"
x + 9 = 13
So to find x we flip the equation
13 - 9 = x
Solve it
4 = x
So the missing number is 4
A postulate is an assumption we use for mathematical reasoning; it isn't yet proven. once it's proven, it becomes a theorem.
Answer:
C
Step-by-step explanation:
It is C. Have a great day!