[tex]1.\\\\3x+3=21\qquad|\text{subtract 3 from both sides}\\\\3x=18\qquad|\text{divide both sides by 3}\\\\\boxed{x=6}\to\boxed{B.}[/tex]
[tex]2.\\\\\dfrac{3}{2}x-4=16\qquad|\text{add 4 to both sides}\\\\\dfrac{3}{2}x=20\qquad|\text{multiply both sides by 2}\\\\3x=40\qquad|\text{divide both sides by 3}\\\\x=\dfrac{40}{3}\\\\\boxed{x=13\dfrac{1}{3}}\to\boxed{B.}[/tex]
