Which best explains why 1-41 = 42?

Jack has a piece of red ribbon that is two times as long as his piece of blue ribbon. he says that he can use two different equation to find out how long his piece of red ribbon is compared to his piece of blue ribbon is. is he correct? explain his reasoning

When y’all answer can y’all explain too !

Using the figure below, select the two pairs of alternate interior angles. a: point 1 and point 4 b : point 2 and point 3 c: point 6 and point 6d: point 5 and point 7