Step-by-step explanation:
5x+3x-14=180
8x-14=180
8x=180+14
8x=174
x=174/8
x= 21.75°
if x is 21.75°, then 5x is 108.75°
which means 3x-14 is 51.25°
therefore, f +108.75+51.25=180
f = 180-160
f=20°
