In this I assumed the expression to be

X + 9 = 2X (X is the amt)

At 27 she earned 25125

At 63 we want to know the cost

As it doubles after 9 years I considered the multiples of 9

2X = 2*25125 and then as per this pattern: 27 36 45 54 63 I did
2X = 2*25125*5

which gives 25125 * 5 *2 = D

In this am i allowed to substitute any no. Wud the ans in all the cases be the same?

How to solve these two

On solving I got

(X-1)(5-1) (3-1)(X-2)

(X-1)4 (2)(X-2)