Answer:
mean of e + f = 18
Step-by-step explanation:
(a + b + c + d)/4 = 9 Multiply by 4
a + b + c + d = 9 * 4 = 36
(a + b + c + d + e + f ) / 6 = 12
but a + b + c + d = 36
(36 + e + f)/6 = 12 Multiply by 6
36 + e + f = 72 Subtract 36 from both sides
e + f = 36 Divide by 2 to find the mean.
(e + f)/2 = 36/2
mean of e + f = 18
