Answer
True
Work Step by Step
Since $x_p$ is a solution to the system $Ax=b$ we have $Ax_p=b$
Obtain $A(y+x_p)=Ay+Ax_p$
Since $y \in nullspace (A) \rightarrow Ay=0$
then $A(y+x_p)=b$
Hence, $y+x_p$ is also a solution the system $Ax=b$
Hence, the statement is true.