To find the measure of each interior angle for an n-sided polygon we use the formula

\(\frac{(n-2) \times 180}{n}\)

for n = 8, p = \(\frac{6 \times 180}{ 8}\)

for n = 6, p = \(\frac{4 \times 180}{ 6}\)

We need to take the difference between the two to get our answer.

\(\frac{6 \times 180}{ 8} - \frac{4 \times 180}{ 6}\)

\(= 135 - 120 = 15\)