One pipe can fill a tank in 12 hours and another can fill the tank in 8 hours. how long would it take to fill the tank using both of the pipes

It will take 4 hours and 48 minutes with both pipes.

Step-by-step explanation:

Add their rates of filling

1st pipe's rate = ( 1 tank ) / ( 12 hrs )

2nd pipe's rate = ( 1 tank ) / ( 8 hrs )

Let, t = hrs to fill tank using both pipes

(1 / 12) + (1 / 8) = (1 / t)

Multiply both sides by 24t

2t + 3t = 24

5t = 24

t = 4.8

0.8 x 60 = 48

It will take 4 hours and 48 minutes with both pipes

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'.