Respuesta :

The answer would be 7.5
[tex]p\%=\dfrac{p}{100}\\\\40\%=\dfrac{40}{100}=0.4\\\\40\%\ of\ B\ is\ 3\\\\0.4B=3\ \ \ |divide\ both\ sides\ by\ 0.4\\\\\boxed{B=7.5}[/tex]