You should try an indirect method.

From the total of possible choices: pick 3 numbers:10C3

subtract the number of choices that you dont want, that would be:

all 3 numbers consecutive:8 possibilities

2 of the 3 numbers are consecutive:there are 9 posibilities to have 2 consecutive numbers, so there are 9*8posibilities for this case.

So, 10C3-8-72=40