Answer the following question, with explanation first.
William read 6 books last month and Brad read thrice as many books as William did. This month, in an effort to catch up, Williams read twice as much as Brad, who read 8 books. Who has read more across the two months, and by how much?

4
Last month Brad read thrice 6 books for a total of 3 * 6 = 18 books.

This month Williams read twice 8 books for a total of 2 * 8 = 16 books.

Across the 2 months Brad has read 18 + 8 = 26 books.

Across the 2 months William has read 6 + 16 = 22 books.

Brad has read 26 - 22 = 4 more books.

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So, the answer is 4