Answer:
x = 11
Explanation:
The mean is found by adding all the numbers and dividing by the number of numbers
x is the unknown number
(3+5+7+9+x)/5 = 7
Multiply each side by 5
(3+5+7+9+x)/5 *5 = 7*5
(3+5+7+9+x) = 35
Combine like terms
24+x = 35
Subtract 24 from each side
24+x-24 = 35 -24
x = 11