Question 644466
<pre>
51,__,__,__,17

51, 51+d, 51+2d, 51+3d, 51+4d = 17
                           4d = 17-51
                           4d = -34
                            d = {{{-34/4}}}
                            d = {{{-17/2}}}
                            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</pre>