Explanation

The total food required for $x$ cows over 150 days is:

$$\text{Total food}=x\times 150$$

When the number of cows is reduced by 10, i.e., $x - 10$, the food lasts for 10 more days, meaning it lasts for 160 days. So, the total food required for x-10 cows over 160 days is:

$$\text{Total food}=(x-10)\times 160$$

Since the total amount of food remains constant in both cases, we can equate the two expressions for total food: x

$$x\times 150=(x-10)\times 160$$