A mechanical device in a workshop produces items at a constant rate of 60 items per

The correct answer is $180$. It’s given that a mechanical device produces items at a constant rate of $60$ items per hour. This rate can be written as $\frac{60 \text{items}}{1 \text{hour}}$. Let $x$ represent the number of items the mechanical device will produce in $3$ hours at the given rate. It follows that $\frac{60 \text{items}}{1 \text{hour}}=\frac{x \text{items}}{3 \text{hours}}$, which can be written as $\frac{60}{1}=\frac{x}{3}$, or $60=\frac{x}{3}$. Multiplying each side of this equation by $3$ yields $180=x$. Therefore, at the given rate, the mechanical device will produce $180$ items in $3$ hours.

Alternate approach: It's given that a mechanical device produces items at a constant rate of $60$ items per hour. At this rate, the mechanical device will produce $\left(\frac{60 \text{items}}{1 \text{hour}}\right)\left(3 \text{hours}\right)$, or $180$ items in $3$ hours.