You actually have most of the answers correct.
E is the origin
D is the x axis
A is the y axis
B is at coordinates (1, 3)
C is at coordinates (3, 1)
*remember you go across on the graph x axis and then up y axis.
X=7 so that means replace all the x values with 7
7^3+5(3)= the answer solve it
7 square 3 + 5 times 3 equal
Let x is the side of the square
so A = x * x or A = x^2 = 36
As you know 36 is a perfect square root = 6^2
Then x = 6 cm
Perimeter = 4x = 4(6) = 24 cm