Question

.... .... .....=30
fii the blanks for using 1,3,5,7,9,11,13,15

Answer 1

 possible only in case of factorial.

3!+1+3+13+7=30 

3!+3!+3!+3!+3!=30

11+1+3+15=30

3! + 15 + 9 = 30

Answer 2

as it is not possible to get an odd number by adding odd no.s odd no.of times, we could do it by using factorials,for example:
11+13+3! -=30
[ by this way,you may also find other combinations ]