You know the triangle has a base of 6 meters, and that the formula to find the area of a triangle is 1/2bh or one-half of the base times the height. So, you would plug in 9 meters squared=one half of six times h, or 9m^2=1/2(6)*(h). In simplifying this, you would get 3h=9m^2. Divide both sides by three and get h=3. Hope this helps, and if you need any further explanations, please let me know!
I not that good with math but I would say C.
As we already have the model that describes the change of the population in Italy in terms of the years that have elapsed, we only have to replace the conditions that are requested in that equation.
Therefore to find the population of Italy in the year 2000 (t = 10 years) substitute t = 10 in the equation and have:

million people
To find the population of Italy in 2008 (t = 18 years)
substitute t = 18 in the equation and have:

million people
To predict the population in Italy for 2015 and 2020 with this model, we substitute in the equation t = 25 and t = 30
t = 25
million people
t = 30
million people