Answer :
Answer:
she started with 50 marbles
Step-by-step explanation:
The total is 100 than you just subtract 20 and 30 becasue that is what is added later on. After you subtract 20 and 30 from 100 you will get 50. Therefore Sara had started out with 50 marbles.
Hope that helps :)
Answer: 50 marbles
Step-by-step explanation: Working backwards we ended with 100 marbles so subtracting the 30 marble we're told she bought at the store and subtracting an additional 20 marbles she received for her birthday leaves her with 50 marbles or mathematically 100-30-20=x where x=50