For "Hình 35," it appears you're asked to perform some geometric calculations based on the figure. Here’s how you might approach each part:

**a)** To show that lines \( m \) and \( n \) are parallel, leverage the properties of corresponding angles or alternate interior angles created by the transversal.

**b)** To find the angle \( \hat{A} \), you can use the properties of angles formed by parallel lines and a transversal. For example, if \( \angle ACB \) is given as \( 72^\circ \), then \( \hat{A} \) can be determined using the relationship between the angles.

**c)** To calculate \( \hat{C} \), use the angles around point \( C \) (the sum of angles in a triangle or straight line can be helpful).

If you have specific measurements or more context, I could guide you through the calculations!