In a month of November, a dance troupe had 150 members
In December there was 20% decrease in the members
In January there was 20% increase from the month before
so you find 20% of 150 which is 30 and because it is a decrease then you would do 150 minus 30 and that is 120. you would now find 20% of 120 and that is 24 so you do 120 plus 24 and that is 144.
