\(15-2\left(2x+1\right)=8+3x\\ \Leftrightarrow15-4x-2=8+3x\\ \Leftrightarrow-4x-3x=8-15+2\\ \Leftrightarrow-7x=-5\\ x=\dfrac{5}{7}\)
\(15-2\left(2x+1\right)=8+3x\)
\(2\left(2x+1\right)=15-\left(8+3x\right)\)
\(2\left(2x+1\right)=7-3x\)
\(4x+2=7-3x\)
\(7x=5\)
\(x=\dfrac{5}{7}\)