Answer: He sold 10 pounds of cashews .
Step-by-step explanation:
Since we have given that
Selling price of walnuts = $4.00 a pound
Selling price of cashews = $7.00 a pound
Number of pounds of walnuts = 10
Let number of pounds of cashew be x
Total price at which he sold a mixture = $5.50
According to question,
[tex]10\times 4+x\times 7=(10+x)\times 5.50\\\\40+7x=55+5.5x\\\\7x-5.5x=55-40\\\\1.5x=15\\\\x=\frac{15}{1.5}\\\\x=10[/tex]
Hence, he sold 10 pounds of cashews .