Answer
a) 40 pink mints
b) 41 pink mints
Work Step by Step
a) P(yellow then pink) = P(green then yellow)
Let $x$ be the number of pink mints, so $80-x$ is the number of green mints.
$20/100 * x/99 = (80-x)/100 * 20/99$
$20*x/9900 = (80-x)*20/9900$
$20x/9900 = 1600-20x/9900$
$20x = 1600-20x$
$40x = 1600$
$40x/40 = 1600/40$
$x = 40$
b) P (yellow then pink) > P (green then yellow)
$20/100 * x/99 > (80-x)/100 * 20/99$
$20x /9900 > (80-x)*20/9900$
$20x > 1600 -20x$
$40x > 1600$
$40x/40 > 1600/40$
$x > 40$
