A herd of 100 cows have food for 30 days. If 20 more cows are added. How long will the food last

This is an indirectly proportional relation, because the food will last less if the number of animals increases.

What we can do is a rule of three, as we know that the food lasts 30 days for 100 animals, and we want to know how many days does it last for 120:

30 days -- 100 cows

 x days -- 120 cows

As it's an inderect rule of three, x = = 25.

The food will last 25 days for them.

c

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c

step-by-step explanation:

b.-4 units

all you   do is count how many times you move