1 pound = 1/14 stone
[multiply by 14]
14 pounds = 1 stone
[multiply by 3]
42 pounds = 3 stone
[divide by 4]
42 / 4 pounds = 3/4 stone
[simplify]
21 /2 = 10.5 pounds = 3/4 stone
You would solve using elimination.
y=1
x=-1
This would be a percent increase, so the formula would be:
New amount - Original amount / Original amount
Replace the numbers:
440 - 154 / 440
Simplify.
286 / 440
The chance would be 0.65, or 65%.