Since the lines intersect, the angles have the following relationships:
- Angles A and C are opposite angles (vertical angles), which means they are equal: \( m∠A = m∠C \).
- Angles A and B are adjacent angles that are supplementary, meaning their measures add up to 180°: \( m∠A + m∠B = 180° \).
Given that \( m∠C = 75° \), we can use the relationship with angle A: \[ m∠A = m∠C = 75° \]
Thus, the measure of angle A is: \[ m∠A = 75° \]
The answer is 75°.