Adam = £500
Beth = £130.
Let the money Adam gives Beth be x.
So Adam would have 500 -x.
Beth would then have 130 + x.
Adam now has twice as much as Beth.
500 - x = 2*(130 + x)
500 - x = 2*130 + 2*x
500 - x = 260 + 2x
- x - 2x = 260 - 500
-3x = - 240
x = -240/-3
x = 80
So Adam gave £80 to Beth.
To find the %: (80 / 500) * 100%. Use your calculator.
= 16 %.
So Adam gave away 16% of his money to Beth.