Remember that
the sum of the interior angles in any polygon is equal to
S=180(n-2)
where
n is the number of sides of polygon
In this problem
we have
n=6 (hexagon)
so
substitute
S=180(6-2)
S=720 degrees
step 2
Adds the interior angles
720=120+(5x-6)+(4x+14)+(7x)+(8x-8)+(6x)
solve for x
combine like terms
720=30x+120
30x=720-120
30x=600
x=20