<span>{x | x I, x ≤ 0}
because I is the Integers</span>
Total no. of buttons = 300 + 700 + 1000
+ 500 = 2500
Possibility for a person to pick a pink button = 300/2500 = (3/25)%
Amount of pink buttons she can expect her friends to pick = 50(3/25) = 6
She can expect to make 6 pink barrettes.