we can convert 35% directly to a decimal:
35% = 0.35
Then, doing the calculation by hand or with a calculator, we find
35% of 300 = 0.35 x 300 = 105.0
So the final answer is
35% of 300 = 105
So, 105 students don't have any siblings.
I hope I helped!
Edit: since it is how many have siblings, you would now
subtract 105 from 300
getting 195
so, 195 students have siblings.