Sorry if I did not address your steps exactly but I think you can make it work, you want to solve for steve first:
K(evin) = S(teve) + 4
K = S+4 (we know kevin ran 4 more miles than steve)
K + S = 26 ( we know that kevin and steve ran 26 miles total)
S+ 4 + S = 26 (substitute K for S+4 which we defined above)
2S + 4 = 26
2S = 22
S = 11 (Steve ran 11 miles)
K = S + 4 = 15
15 + 11 = 26 miles. Hope this helps.
