a) The model of the linear equation is:
[tex]\begin{gathered} y=0.6t+7.6 \\ \text{Please note that 'y' is in millions} \end{gathered}[/tex]b)
[tex]\begin{gathered} \text{from 2009 to 2018 is 9years} \\ t=9 \\ \text{Substituing for t=9 in the modelled equation, we have:} \\ y=0.6(9)+7.6 \\ y=5.4+7.6 \\ y=13\text{ million} \end{gathered}[/tex]c)
[tex]\begin{gathered} y=0.6t+7.6 \\ 17.2=0.6t+7.6 \\ 17.2-7.6=0.6t \\ 9.6=0.6t \\ t=\frac{9.6}{0.6} \\ t=16 \\ \text{Adding 16years to the base year (2009), thus the final answer is 2025} \end{gathered}[/tex]