Answer:
z = -17
Step-by-step explanation:
If the average of x and y is 11, then;
x+y/2 = 11
x+y = 2 + 11
x+y = 22 .... 1
similarly, if average of x, y and z is 5, then;
x+y+z/3 = 5
x+y+z = 3*5
x+y+z = 15
Since x+y = 22
22 + z = 5
z = 5 - 22
z = -17
Hence the value of z is -17
