the correct question is
If a and b are parallel lines, and m∠3 = 128°, what is the measure of ∠8?
see the attached drawing
we have
m∠3 = 128°
m∠3 = m∠7---------------- > Corresponding Angles
180°=m∠7+m∠8---------- > Supplementary Angles
therefore
m∠8=180°-128°=52°
the answer is the m∠8 is 52°