Population in 1990 was 134 million. in 2000 it was 139 million. what was it in 2014

Well first lets find the ROC (rate of change) in the sets of data.
1990 -> 134
2000 -> 139

so lets find the difference from the years given
2000-1990=10  so there is a 10 year gab
139-134=5  so there is a 5 million increase in the population 

so divide 10 by 5 which gives us 2, so every year there is a 2 million increase in the population. so from 2000 to 2014 there is 14 years, so 
14 x 2= 28, then add that to the latest population data
139+28=167
so the population in 2014 would be 167 million 

Hope this helped!!