Say the percentage increase is 25%. If you have the whole number of 30 then you would multiply 30 by .25. You should therefore get 7.5 once both are multiplied. That means you should add 7.5 to 30, and your final answer will be 37.5.
Step-by-step explanation: The question tells us that the population decreases by 1/4 every single year. That means, since 1/4 equals .25, the population decreases by 25% every year :)
