The first step is to solve this equation for t. To do this, we have to isolate t and bring p to the right side of the equation:
[tex]\begin{gathered} p=25.5t+645 \\ -25.5t=-p+645 \\ t=\frac{p}{25.5}-\frac{645}{25.5} \\ t=0.0392p-25.2941 \end{gathered}[/tex]We can now plug in p = 1385 and solve for t:
[tex]\begin{gathered} t=0.0392(1385)-25.2941 \\ t=54.3137-25.2941 \\ t\approx29 \end{gathered}[/tex]We know that t is the number of years AFTER 1990, so the year we are looking for is 1990 + t, which is 1990 + 29 or 2019