This problem can't be solved by integer. Because 1, 3, 5, 7, 9, 1 1 3, 15 are all odd numbers, according to the calculation law: "odd+odd = even, even+odd = odd", one of the three odd numbers. And 30 is an even number, so according to the conventional method, it is impossible to add 30 by adding three integers.

3. This question examines the comprehensive ability of mathematics, mainly divergent thinking.