A pen cost $4 and a book costs $7. Sam paid $64 for 10 such pens and books. Find the number of pens and the number of books he had bought.

Answer 1

Let's assume the number of pens that Sam bought is "x".
Therefore, the number of books that Sam bought would be "10 - x".

The cost of x pens would be 4x dollars.
Similarly, the cost of (10 - x) books would be 7(10 - x) dollars.

Since the total cost was $64, we can create the equation:
4x + 7(10 - x) = 64

Expanding the equation, we get:
4x + 70 - 7x = 64
-3x + 70 = 64

Subtracting 70 from both sides:
-3x = -6

Dividing both sides by -3:
x = 2

Therefore, Sam bought 2 pens and the number of books he bought is 10 - 2 = <<10-2=8>>8. Answer: \boxed{2, 8}.