Explanation:
x = Alice's money
y = Mio's money
z = Grace's money
x + y + z = sum
there are originality 5+4+3 = 12 parts of the money shared between them.
x = 5/12 sum
y = 4/12 sum
z = 3/12 sum
after the money transfer we are only having 4+3+2 = 9 parts of the same money distributed.
so, we are dealing with 1/9 parts.
let's bring everything to 1/36 to be able to truly compare things.
therefore
x = 15/36 sum
y = 12/36 sum
z = 9/36 sum
15/36 sum + 10 = 16/36 sum
because 4/9 = 16/36
10 = 1/36 sum
sum = 10×36 = £360
so, together they have £360.
and they had before the £10 transfer £150, £120, £90.
after the £10 transfer they had £160, £120, £80.