Name the property used in the following: 1. if m + n = p, then m + n + 3 = p+3
2. If a = 8, then a-3=5
3. If 2x = z, and z=y, then 2x = y

(paki answer ng maayos please) ​

When keisha installed a fence along the 200 foot perimeter of her rectangular back yard, she left an opening for a gate.in the diagram below, she used x to represent the length in feet of the gate? what is the value? a. 10 b. 20 c. 25 d. 30