The perimeter is the sum of all the sides, so P = (5x -7) + (3x-4) + (2x -6). Then group like terms so you have p = 5x + 3x + 2x -7-4-6 and end up with P = 10x - 17
Yes because it is the amount you are studying.
It is usually in Meaga Bytes per second.
MB/s depending on the speed of your Internet.