Correct probability : 3/7
To find the correct probability, Noura needs to count ALL of the times she tossed the coin. To find that we just add 15 + 20, which equals 35.
Then to calculate the probability she will get heads is out the number of heads landed over the amount of times the coin was flipped.
15/35
We then simplify this fraction by dividing the top and bottom both by 5.
This leaves us with the answer of 3/7.