Two parallel lines are cut by transversal. If one angle is 75°, how many angles of 105° are form?

When two parallel lines are cut by a transversal, a total of eight angles are formed. These angles will either be equal to the given angle or supplementary to it.

Given one angle is $75^\circ$. The angles that are supplementary to it will add up to $180^\circ$.

So, the other type of angle formed is $105^\circ$.

Out of the eight angles formed, four will be equal to the given angle ($75^\circ$), and the other four will be equal to its supplementary angle ($105^\circ$). This is because there are two sets of vertically opposite angles at each intersection, and corresponding angles are equal.

Therefore, there are 4 angles of $105^\circ$ formed.

The number of angles of $105^\circ$ formed is $\boxed{\text{4}}$.