In order to find a discounted price you subtract the discount percentage as a decimal from 1 and multiply the outcome to the original price. For this case, 1-0.25=0.75 and 1-0.1=0.90. So your equation will be 69(0.75)(0.90)
The current population (in 2005) is 4000 because it is the constant. The slope tells us how many people are added to the population, so 70 per year. For ex. 2008 (2008- 2005 = 3=> 3 x 70 = 210 => 210 + 4000 = 4210).
