all 3 angles add up to 180 so we know
40+30=70.
180-70=110
13x+6=110 now we need to remove the six so subtract it by itself but you also need to remove 6 from 110 to make up for it
13x=104 now divide 13 from both numbers
13x/13 =x 104/13=8
so x=8 or f=8
To make sure its correct 13*8+6=110
110+40+30=180
