Luis needed to buy some socks. He bought 4 pairs of red socks and 6 pairs of blue ones. In total, he spent $42. If the red socks cost $3 each, how much did he pay for each blue pair?
Step-by-step reasoning process below:
5
Let B be the cost of the blue socks.

4 * 3 + 6 * Y = 42.

12 + 6 * Y = 42.

6 * Y = 30.

Y = 5.

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So, the final answer is 5