Abcd is a rectangle. find the length of each diagonal.

The diagonals of a rectangle are congruent, so AC = BD

c/3 = 4-c
с = 3(4-с)
с = 12 - 3с
с + 3с = 12
4с = 12
с = 12/4
с = 3

АС = с/3 = 3/3 = 1
BD = 4 - с = 4 - 3 = 1

The length of each diagonal = 1