Perimeter is the addition of all 4 sides and a square as all the same sides. so every side will be the same. so if you divide 216 by 4 you get 54. you can check this by adding 54+54+54+54=216 or 54x4=216
If you mean "how to write the sum", the answer is

The result of this sum is
, because you start from 2 on the number line and take 3 steps to the left (negative integers mean going left, positive integers mean going right)
The distance formula is d=√(x2-x1)² + (y2-y1)²
So... d =8.06226
Hope this helps
Divide 45 and 9 it was give you -5
1: You are looking to find the mps increase over a second
2: 45 m/s from 0 m/s in 10 secs that is 4.5 m/s per second
3: The acceleration is 4.5m/s