A group of five students took a test. Another student joins later; with her marks included, the group's average score goes up by 2. How many marks above the average (without her) did she score?

1. Let the old average of 5 students be a. New total of 6 = 5a + x and new average = a + 2. 2. (5a + x)/6 = a + 2 gives x = 6a + 12 − 5a = a + 12. 3. Her marks above old average = x − a = 12. _Source: RRB Group D CEN-02/2018 PYQ, Q.49._