Answer:
[tex]\huge\boxed{b=\dfrac{24}{5}\to b=4\dfrac{4}{5}\to b=4.8}[/tex]
Step-by-step explanation:
[tex]12=\dfrac{5}{2}b\to\dfrac{5}{2}b=12\qquad|\text{multiply both sides by 2}\\\\2\!\!\!\!\diagup\cdot\dfrac{5}{2\!\!\!\!\diagup}b=12\cdot2\\\\5b=24\qquad|\text{divide both sides by 5}\\\\\dfrac{5b}{5}=\dfrac{24}{5}\\\\b=\dfrac{24}{5}\to b=4\dfrac{4}{5}\to b=4.8[/tex]