t^2 - 3t - (2t^2 + 7t - (2t^2 - 11t - 3 + (3t^2 - 23t - 12))) =
= t^2 - 3t - (2t^2 + 7t - (2t^2 - 11t - 3 + 3t^2 - 23t - 12)) =
= t^2 - 3t - (2t^2 + 7t - (5t^2 - 34t - 15)) =
= t^2 - 3t - (2t^2 + 7t - 5t^2 + 34t + 15) =
= t^2 - 3t - (- 3t^2 + 41t + 15) =
= t^2 - 3t + 3t^2 - 41t - 15 =
= 4t^2 - 44t - 15