a) \(\left(x+2\right).\left(x+3\right)-\left(x-2\right).\left(x+5\right)=6\)
\(\Leftrightarrow\left(x+2\right).x+\left(x+2\right).3-x.\left(x+5\right)+2.\left(x+5\right)=6\)
\(\Leftrightarrow x^2+2x+3x+6-x^2-5x+2x+10=6\)
\(\Leftrightarrow2x+16=6\)
\(\Leftrightarrow2x=-10\)
\(\Leftrightarrow x=-5\)