According to ques,
Points are : \[\left( 2,\text{ }\text{ }1,\text{ }\text{ }3 \right)\text{ }and\text{ }\left( 1,\text{ }\text{ }3,\text{ }3 \right)\]
And,
Direction ratios of the normal to the plane are: \[\left( 1\text{ }+\text{ }2,\text{ }-3\text{ }+\text{ }1,\text{ }3\text{ }+\text{ }3 \right)\text{ }=\text{ }\left( 3,\text{ }-2,\text{ }6 \right)\]
Again,
the equation of plane passing through one point (x1, y1, z1) is
\[a(x\text{ }\text{ }{{x}_{1}})\text{ }+\text{ }b(y\text{ }\text{ }{{y}_{1}})\text{ }+\text{ }c(z\text{ }\text{ }{{z}_{1}})\text{ }=\text{ }0\]
Or,
\[3\left( x\text{ }\text{ }1 \right)\text{ }\text{ }2\left( y\text{ }+\text{ }3 \right)\text{ }+\text{ }6\left( z\text{ }\text{ }3 \right)\text{ }=\text{ }0\]
Or,
\[3x\text{ }\text{ }3\text{ }\text{ }2y\text{ }\text{ }6\text{ }+\text{ }6z\text{ }\text{ }18\text{ }=\text{ }0\]
Or,
\[3x\text{ }\text{ }2y\text{ }+\text{ }6z\text{ }\text{ }27\text{ }=\text{ }0\Rightarrow 3x\text{ }\text{ }2y\text{ }+\text{ }6z\text{ }=\text{ }27\]
hence, the required equation of plane is
\[3x\text{ }\text{ }2y\text{ }+\text{ }6z\text{ }=\text{ }27.\]