Linear dependence of vectors

Given two vectors \vec{V_1}= 6\hat{x}+4\hat{y}+2\hat{z} and \vec{V_2}= 10\hat{x}-5\hat{y}+3\hat{z}:
Find \vec{V_3} such that  \vec{V_1}+\vec{V_2}+\vec{V_3}=0.
Find \vec{V_3} such that  \vec{V_1}-\vec{V_2}+\vec{V_4}=0.