Answer:
1/3
Explanation:
We are given ...
barrettes : hair ties = 5 : 7
barrettes : hair bands = 5 : 8
Then the combined ratios are ...
barrettes : hair ties : hair bands = 5 : 7 : 8
For every 5 barrettes, there are 7+8 = 15 hair ties and bands, so their ratio is ...
barrettes/(hair ties and bands) = 5/15 = 1/3