Knowing that a straight line is 180° you can use this to your advantage. If you take all parts of the ratio and add them together you can get the total number of "pieces" the 180° will be divided into. [tex]4 + 3 + 2 = 9[/tex] Then divide the 180° by the total. [tex]180 \div 9 = 20[/tex] Now you can use the value for one "piece" and multiply it by how ever many the ratio says.
The angle FOG has the 4 value of the ratio so you multiply 20 by 4 to get the value of the angle. [tex]20 \times 4 = 80[/tex] m<FOG = 80°
