1/4 if the T-shirts are purple.
to answer this, you need to find the greatest common denominator
1/2=2/4
1/4=1/4
2/4 plus 1/4 is 3/4 t-shirts.
2/4+1/4=3/4
so, u subtract the total amount of t-shirts(4/4 t-shirts) with the amount of pink(1/4 t-shirts) and white(2/4 t-shirts), which u get 1/4 purple t-shirts.
4/4-3/4=1/4
so, pat has 1/4 purple t-shirts.