Add up all the numbers the divide by the amount of numbers in the set.
1199/11 = 109
B. 109 answer
It's "commutative property," which says that (for addition/multiplication) order of the operator doesn't matter. For eg, 3 * 5 = 5 * 3.
Associative property (again, of multiplication and addition) means that it doesn't matter how you solve an expression if the same operand is used and some numbers are grouped. For eg. 3 * (5 * 4) = (3 * 5) * 4.
Answer:

Step-by-step explanation:
The formula of the circumference of a circle is
.
The length of an arch can be found by using the ratio of circumference to the arc.
First, find the circumference of the circle:

Then you find the ratio:
The length of the arc is 90/360, which is 1/4, of the circumference.
Finally, find the length of the arc:
or 
I hope this helps :)