167. To transport 60 tons of cargo from one place to another, a certain number of trucks were required. Due to the poor condition of the road, each truck had to carry 0.5 tons less than originally planned, which is why 4 additional trucks were required. How many trucks were initially required?
Solution. Let $x$ be the original number of trucks. Then, each truck was supposed to carry $\frac{60}{x}$ tons of cargo, but they carried $\left(\frac{60}{x}-0.5\right)$ tons each. Since all 60 tons were loaded with the help of four additional trucks, we have the equation

$$
\left(\frac{60}{x}-0.5\right)(x+4)=60, \text{ or } x^{2}-4 x-480=0 \text{. }
$$

Solving the obtained quadratic equation, we find $x_{1}=-24$, $x_{2}=20$.

Since only the positive root satisfies the condition of the problem, we have $x=20$.

Answer: 20 trucks.