The perimeter of an equilateral triangle exceeds the perimeter of a square by 1989cm. The length of each side of the triangle exceeds the length of each side of the square by d cm. The square has perimter greater than 0. How many positive integers arenotpossible values for d?

t for side of triangle s for side of square

3t = 4s + 1989

t - s = d

t= s +d

3s + 3d = 4s + 1989

3d = s + 1989

d = s/3 + 663

it doesn't seem to make sense.

Pls help.