Between 2000 and 2015, the number of twin births in the United States increased by 13%, to approximately 135,000. About how many twin births were there in 2000?
Let the number of twin births in 2000 ==T
T x 1.13 == 135,000
T ==135,000 / 1.13 ==119,469 - approx. number of twin births in 2000