Question

the country's population in 1994 was 98 million.in 2001 it was 103 million estimate the population in 2018.round to the nearest million

Answer 1

Populations generally increase as an exponential function.  In a short period of time, it could be approximated as linear (first degree).  Depending what your teacher expects, 

Linear model:
rate of increase = (y2-y1)/(x2-x1)=(103-98)/(2001-1994)=5/7 million per year.
From 2001 to 2018, there are 17 years.  So add 17(5/7) millions to population of 2001.

exponential model:
Over 7 years, the ratio of populations is 103/98, so the annual ratio is (103/98)^(1/7)=1.007134, about 0.7134%.
Use the compound interest formula to find the population growing at the same rate from 2001 for 17 years:
population at 2018 = 103 millions * 1.007134^17 which is a little over 116 millions.

Answer 2

Plato Answer

116 million