What number should be subtracted from each of 50, 61, 92, 117 so that the numbers, so obtained in this order, are in proportion?

Let the number subtracted be x. For proportion: (50-x)/(61-x) = (92-x)/(117-x). Cross-multiplying: (50-x)(117-x) = (61-x)(92-x). Expanding: 5850 - 50x - 117x + x² = 5612 - 61x - 92x + x². Simplifying: 5850 - 167x = 5612 - 153x. So 5850 - 5612 = 167x - 153x, giving 238 = 14x, hence x = 17. The correct answer is 17.