RRB NTPC CBT 2 Level 6 Exam 9 May 2022 Shift 2

In each of the given number-clusters, the number on the right side of = (the equal to sign) is calculated by performing certain mathematical operations on the three numbers on the left of = (the equal to sign). All three number-clusters follow the same pattern. Select the number from among the given options that can replace the question mark(?) in the third number-cluster.
15, 8, 12 = 10
26, 6, 13 = 12
11, 12, 4 = ?