Answer:
EC = 13
Explanation:
The diagonals of a rectangle bisect each other, thus
EC = EA, that is
6x + 1 = x + 11 (subtract x from both sides )
5x + 1 = 11 ( subtract 1 from both sides )
5x = 10 ( divide both sides by 5 )
x = 2
Thus
EC = 6x + 1 = 6(2) + 1 = 12 + 1 = 13