Answer:
A. 15
Explanation:
To solve this you need to compare the lengths given to you in the question statement.
Because the lines originate from a single point, they're like triangles. We can easily see a triangle AGF and a triangle ADE, right?
Both triangles are similar triangles, so we can see triangle ADE as a larger version of angle AGF.
They give you the dimension of A F and A E (through A F + F E) to establish a ratio... and they give you A G, asking for A D.
So, A F = 16, A E = 20 (16 + 4), A G = 12.
Since A D is to A G what A E is to A F, we can easily make the following cross-multiplication:
So, A D = (A G * A E)/A F
A D = (12 * 20) / 16 = 15