The increase is 25894 - 12000 = 13894 British pounds.
So the question becomes:
13894 is what percent of 12000?
"is" means =
"what" means x
"percent" means /100
"of" means *
13894 = x/100 * 12000
13894 = x * 120
x = 13894/120
x = about 115.78
Answer: 25984 British pounds is an increase of about 115.78% over 10000 British pounds.