The average (arithmetic mean) of a and b is 10, and the average (arithmetic mean) of c and d is 7. If the average (arithmetic mean) of a, b, and c is 8, what is the value of d ? _____
我的答案:
The average (arithmetic mean) of a and b is 10, and the average (arithmetic mean) of c and d is 7. If the average (arithmetic mean) of a, b, and c is 8, what is the value of d ?