Answer:
b = 320
Step-by-step explanation:
a + b = 880
1 - 4/7 = 3/7 (restant A)
1 - 1/4 = 3/4 (restant B)
(3/7) . a = (3/4) . b
a = (7/4) . b
(7/4) . b + b = 880
7b + 4b = 880 . 4
11 b = 880 . 4
If the goal is to break the vases: 3/20 = 15.0% or 0.15
If the goal is to not break the vases: 17/20 = 85.0% or 0.85