In order to find the answer you will have too divide 58 by 18 and then divide what you get from that by 100 to get your answer.
100%/x%=58/18
(100/x)*x=(58/18)*x
100=3.22222222222*x
(3.22222222222) to get x
100/3.22222222222=x
x=31.0344827586
Therefore your answer is "31%."
Hope this helps.