(25%/100) * 24 pieces = 6 pieces
you can also think of it as 25% is 1/4 because percent literally translates to "per hundred"
25 per 100 is written as 25/100 (if you think about speed limits, twenty kilometers per hour is represented as 20 km/h)
reduce 25/100 and you get 1/4 then multiply that by 24 pieces
24 * 1/4 = 24/4 = 6 pieces