Answer:
m∠4 = 40°
Explanation:
Using the vertical angle theorem we can find that...
m∠6 ≅ m∠7


Using this, we know that angle 6 and 8 are supplementary so...
m∠6 + m∠8 = 180°
140° + m∠8 = 180°
m∠8 = 40°
Then, we can use the corresponding angle theorem to find that...
m∠8 ≅ m∠4
m∠4 = 40°