Answer:
The sum of numbers a and b,
i.e., a + b is 18
Explanation:
Given the average (arithmetic mean) of 4, a, b, 6 is 7
Then, according to question,

4 + a + b + 6 =

10 + a + b = 28
a + b = 28 -10
a + b = 18
Therefore, the sum of numbers a and b, i.e., a + b is 18