When x is subtracted from each of 55, 50, 23 and 22, the resulting numbers, in this order, are in proportion. What is the fourth proportion of 3, 7 and x?

Correct option is A

Given:
(55 − x), (50 − x), (23 − x), (22 − x) are in proportion.
Formula Used:
If a, b, c  and d are in proportion then $$\frac{a}{b} = \frac{c}{d}$$
$$\text{Fourth proportional of a, b and c is given by} = \frac{b \times c}{a}$$​​​
Solution:
​$$\frac{55 - x}{50 - x} = \frac{23 - x}{22 - x}\\\ \\(55 - x)(22 - x) = (50 - x)(23 - x)\\\ \\1210 - 77x = 1150 - 73x\\\ \\60 = 4x\\\ \\x = 15\\\ \\$$​​
Fourth proportional of 3, 7, 15 = (7 × 15) ÷ 3 = 35