First you should simplify the inequality and get n by itself:
3n - 10 ≥ 2 Add 10 on both sides
3n ≥ 12 Divide 3 on both sides
n ≥ 4
When the sign is ≤ or ≥ (less/greater than or equal to), the line is a solid line.
When the sign is < or >, the line is a dotted line.
If the variable is > than the function (like y > 3x + 2, or x > 2y²) The shaded area is above the line (or going in the positive direction)
If the variable is < than the function (like x < 2, or x < 5z - 7), The shaded area is below the line.
Since we got n ≥ 4,
If n is an x value, or n = x, you would have a horizontal line at y = 4, but if n is a y value, n = y, you would have a vertical line at x = 4. The shaded area should be above the line, or to the right of the line since n is > 4. (Sorry, I don't know if n = y or n = x, hope this clarified things)