The population is 25000. the population increases 3% yearly. whats the population 10 years from now

Here we can find it by the formula of simple interest 
                               A=P×R×t÷100
                              A=25000×3×10÷100
                              A=2500×3
                             A=7500
Then the population after 10 yrs will be 25000 +7500 = 100000

Population in the zeroth year = 25000

After 1 year it increases to 3%, that is 100% + 3% = 103% = 103/100 = 1.03

So it increases by a multiplying factor of 1.03.

At the end of year 1 = 25000*1.03

At the end of year 2 = 25000*1.03*1.03 = 25000*1.03²

At the end of year 3 = 25000*1.03*1.03*1.03 = 25000*1.03³
...



Similarly at the end of 10 years = 25000*1.03¹⁰       evaluate with calculator.

 = 25000*1.03¹⁰ ≈ 33 597.91

So the population at the end of 10 years will be ≈ 33 598

Hope this explains it.