[tex]-\dfrac{9}{4}v+\dfrac{4}{5}=\dfrac{7}{8}\qquad\text{multiply both sides by common denominator 40}\\\\40\cdot\left(-\dfrac{9}{4}v\right)+40\cdot\dfrac{4}{5}=40\cdot\dfrac{7}{8}\\\\10(-9v)+8\cdot4=5\cdot7\\\\-90v+32=35\qquad\text{subtract 32 from both sides}\\\\-90v=3\qquad\text{divide both sides by (-90)}\\\\v=-\dfrac{3}{90}\\\\\boxed{v=-\dfrac{1}{30}}[/tex]