In [tex] \frac{3}{4} [/tex] hour Manny can make 12 pizzas.
In [tex] \frac{3}{4} * \frac{4}{3} [/tex] hour Manny can make 12 * [tex]\frac{4}{3}[/tex] pizzas
In 4 hours, Manny can make 12 * [tex]\frac{4}{3}[/tex] * 4 pizzas
= 64 pizzas
∴ Manny can make 64 pizzas in 4 hours