Answer
$x^2+6$
Work Step by Step
Since the grouping symbol is preceded by a negative sign, then the sign of each term inside the grouping symbol alters once the grouping symbol is removed. Hence, the given expression, $
3x^2+11-(2x^2+5)
$, is equivalent to
\begin{array}{l}\require{cancel}
3x^2+11-2x^2-5
.\end{array}
By combining like terms, then this simplifies to
\begin{array}{l}\require{cancel}
x^2+6
.\end{array}