\( \definecolor{colordef}{RGB}{249,49,84} \definecolor{colorprop}{RGB}{18,102,241} \)
A school plants \(5\) trees in its garden to start. Every year, they plant \(3\) new trees.
Let \(u_n\) be the total number of trees after \(n\) years.
  1. Find the explicit formula for \(u_n\).
    \(u_n=\)
  2. How many trees will there be after \(12\) years?
    trees