51,__,__,__,17 51, 51+d, 51+2d, 51+3d, 51+4d = 17 4d = 17-51 4d = -34 d = d = d = -8.5 Sio the numbers are 51, 51+(-8.5), 51+2(-8.5), 51+3(-8.5), 17 51, 42.5, 34, 25.5, 17 Edwin