The given linear equation is 2x + cy = 8 .........(i)
By the given condition, x and y-coordinate of given linear equation are same. i.e x = y
Put y = x in the equation(i). we get,
2x+cx=8
⇒cx=8−2x
c=8−2xx,x≠0
Hence, the required value of c is 8−2xx.