When a fraction describes part of a group, the denominator tells you how many equal units the group splits into. Always find ONE unit first — divide the total by the denominator — then multiply for however many units you need. The P6 twist is a fraction OF THE REMAINDER: after some is spent, the next fraction is taken from what is left, not from the original amount. Reading which whole a fraction refers to is most of the work.
Worked example
Problem 2/5 of the 40 marbles in a box are red. How many marbles are red?
The 40 marbles are the whole, split into 5 equal units, because the denominator is 5.
Find one unit: 40 ÷ 5 = 8.
The red ones are 2 of those units: 8 × 2 = 16, so there are 16 red marbles.
Tip Find ONE unit first — every fraction-of-a-set question turns on that single step.