Answer:
(18,−21)
Explanation:
Dilation: multiply each coordinate
(x,y)\rightarrow (3x,3y)
(x,y)→(3x,3y)
Dilations multiply by scale factor
(\color{red}{6},\color{blue}{-7}) \rightarrow (3\cdot \color{red}{6},3\cdot \color{blue}{-7})=\mathbf{(18,-21)}
(6,−7)→(3⋅6,3⋅−7)=(18,−21)