Answer: 21cm longer.
Step-by-step explanation:
1. Y/R = 7cm, B/R = 7(4)cm
2. B/R = 28cm
3. 28cm - 7cm: as you are trying to find out how longer the b/r is relative to the y/r.
4. 28 - 7= 21cm.
In conclusion, the blue ribbon is longer than the yellow ribbon by 21cm.
