<human>:  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?
<bot>: Define a variable ** Let B be the cost of the blue socks
Write an equation ** 4*3 +6*Y =42
Combine like terms ** 12 + 6*Y=42
Subtract 6 from both sides ** 6*Y =30
Divide by 6 ** Y = <<5=5>>5
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