<span>"3 ≤ x ≤ 7 or x is between 3 and 7, inclusive"
The domain of a function is the range of values for which the function is defined. Since your function is a graph, look at the minimum and maximum values of X for that graph. The graph is a straight line connecting (3,2) to (7,12). So the legal values of X are every value between 3 and 7. And since the value 3 exactly is acceptable as well as the value 7 being acceptable, then the range is from 3 to 7 inclusive. Now look at the available answers and you'll see that
"3 ≤ x ≤ 7 or x is between 3 and 7, inclusive"
is one of the available choices and it's correct.</span>
