3. Identify the property used: (9+4) +7=(4 + 9) +7 A. Commutative Property of Addition
B. Associative Property of Addition
C. Distributive Property
D. Identity Property

B. Associative property of addition.

Step-by-step explanation:

The identity property involves zeros, so we know it's not that one.

The distributive property is when you have a number, and then two other numbers in parenthesis and you multiply the numbers by the number outside the parenthesis. (ex: 4(1 + 3) you would do 4 x 1 and 4x 3 and add them together) and we know it's not that one because it doesn't show the distribution.

The associative property states that you can re-group numbers and you will get the same answer, and since it has parenthesis, we know it's this one.

The commutative property states that you can move numbers around and still arrive at the same answer.

for the friend request.

when a figure, such as triangle (xyz) is reflected over the line y = x to create x'y'z' the x-coordinates and y-coordinates of the original image (pre-image) will be reversed for the image. (e.g., (x, y) > (y, x)) this means that the pre-image position of the x- and y-coordinates switch places which in turn provides a mirror like image of the original xyz.  

i notice that when i draw a line segment from x to x', that the points are parallel from each other -- they are exactly across from each other and do not intersect with any other points.  

yes, think i would see the same characteristic if you drew the line segment connecting y with the reflecting line and then y' with the reflecting line because of the essence of reflections. because it is a mirror image, each point was effected the same way which leads me to conclude that they same would apply to y and y'.