The correct answer is C
Explanation
Let r equal the weight of each rock, in ounces. The weight on one side of the scale is (6 times r) + 10 ounces and the weight on the other side is (4 times r) plus 22 ounces. Since the two weights balance, you can write the equation (6 times r) +10 = (4 times r) + 22. Solving this equation yields r equals 6.