Milton has some books about zoology and 4 times as many books about botany. If he has 80 books total, how many zoology books does he have?
Step-by-step reasoning process below:
16
Let z be the number of zoology books and b be the number of botany books.

We know that z + b = 80 and b = 4z.

Substituting the second equation into the first equation, we get z + 4z = 80.

Combining like terms, we get 5z = 80.

Dividing both sides by 5, we get z = 16.

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The answer: 16