What 3 things does these shapes have in common

If chord ab is congruent to chord cd, then what must be true about ef and eg?

Erin bought christmas cards for $2 each to send to her family and friends. which variable is the dependent variable?

There are three bags: a (contains 2 white and 4 red balls), b (8 white, 4 red) and c (1 white 3 red). you select one ball at random from each bag, observe that exactly two are white, but forget which ball came from which bag. what is the probability that you selected a white ball from bag a?