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9514 1404 393
Answer:
x = 18
Step-by-step explanation:
The parallel lines cut the transversals proportionally.
(2x -1)/40 = 21/24
2x -1 = 35 . . . . . . . multiply by 40
2x = 36 . . . . . . . . add 1
x = 18 . . . . . . . . . divide by 2