Explanation:
it made £12,858.56.
the costs were £6,429.28
so, the profit was
12,858.56 - 6,429.28 = £6,429.28
since cost and profit are equal, that means they are both exactly half of the total income.
and half means 50%.
formally, to do the full % calculation :
100% = 12,858.56
1% = 100%/100 = 12,858.56/100 = 128.5856
how many % are 6,429.28 ?
as many % as times that 1% fits into 6,429.28 :
6,429.28 / 128.5856 = 50
so, it is 50%.