Question

+ + +=30 use only these numbers1,3,5,7,9,11,13,15

Answer 1

15+13+1+1=30 may be the answer
there is no answer to this question as adding 3 odd numbers will give a odd number so its not possible... 
but we can do it like this
15+13[1x2]=30

Answer 2

(11-1)+(13-3)+(15-5)=30!!