What is the next number in the sequence 5 10 3 15 20 13 25 30?

We are asked to determine the next numbers in the given sequence such as 5 10 3 15 20 13 25 30. In order for us to answer this problem, we need to find the difference between the two consecutive number and perform subtraction such as shown below:
For 5 and 10, the difference is -5
For 10 and 3, the difference is 7
For 3 and 15, the difference is -12
For 15 and 20, the difference is -5
For 20 and 13, the difference is 7
For 13 and 25, the difference is -12
For 25 and 30, the difference is -5

Now, we can identify the next two numbers in the sequence since we already know that the format of the difference is -5, 7 and -12. So the next numbers are the following:
30 - 7 = 23
23- (-12) = 35

Therefore, the sequence is 5 10 3 15 20 13 25 30 23 35