Question

_+_+_=30
we can use only 1,3,5,7,9,11,13,15
you can also repeat number

Answer 1

There are many mock answers to this question, but a logical answer has not yet been found.
1hr+5hr+1day=30hr

Proof that this question is not mathematically solvable unless it is a riddle
Take any number, say "x". In the expression $y=x$, y could be either odd or even. To make it even, we change the expression to $y=2x$.
Here, y is an even number since $y=2x$ and every even number is a multiple of 2 and every multiple of 2 is an even number.
Even here, only y is an even number. "x" could might as well be an odd number. But even if so, a perfect double or a multiple of 2 is always an even number.
Then, if the expression $y=2x$ is an even number indeed, then the expression $y=2x+1$ or $y=2x-1$ will be odd since every even number is succeeded and preceded by an odd number. Since 30-1 or 30+1 are not even, $y=2x +1$ or $y=2x-1$ will never be 30.