15 % of the total amount (18k€)
He misinterpreted your unclear statement ^^ 18k / 15 % x 100 % x = 120 k
Then maybe I expressed myself incorrectly. Sorry.
(18,000 / 100) * 15 = 2700
EDIT: But you calculate 18,000 * 15 % or 18,000 * 0.15
Regards
Steven