Explanation:
930 = -20×|t - 15| + 1010
one solution is for (t - 15) > 0
930 = -20×(t - 15) + 1010
-80 = -20×(t - 15)
4 = t - 15
t = 19
that means 2019.
the second solution is for (t - 15) < 0
930 = 20×(t - 15) + 1010
-80 = 20×(t - 15)
-4 = t - 15
t = 11
that means 2011.