Answer:
3/10 or 30%
Explanation:
So the mom was 35 when she had her kid. When the kid is 15, that would make the mom 50 (35+15).
Then just divide! The term "fraction" is just a confusing term that most of the time means to divide.
15/50 is 3/10. If you want it as a percentage, then multiply the whole thing by 10/10, which gives you 30/100, or 30% of her mom's age. Hope this helped!