Problems based on Numbers Test 3

Let the number of column = x
Number of rows = x + 4
Each bench is seated with 5 students.
Two seats are vacant in class of 158 students.
According to the statement,
$5\left(\mathit{x}\right)\left(\mathit{x}+4\right)=158+2$
$5{\mathit{x}}^2+20\mathit{x}=160$
$5{\mathit{x}}^2+20\mathit{x}-160=0$
${\mathit{x}}^2+4\mathit{x}-32=0$
${\mathit{x}}^2+8\mathit{x}-4\mathit{x}-32=0$
$\mathit{x}\left(\mathit{x}+8\right)-4\left(\mathit{x}+8\right)=0$
$\mathit{x}=-8,4$
$\mathit{x}=4$
Number of rows $=\mathit{x}+4=4+4=8$.