If the point A(m, n) is first reflected in the y-axis and then reflected in the x-axis to the point A"(-10, 15), then the value of (m - n) is :

1. -25

2. -5

3. 5

4. 25

Given, point A(m, n).

On reflection in y-axis, the sign of x-coordinate changes,

(m, n) ⇒ (-m, n)

On reflection in x-axis, the sign of y-coordinate changes,

(-m, n) ⇒ (-m, -n).

Given,

Final coordinates = A"(-10, 15)

∴ (-m, -n) = (-10, 15)

⇒ -m = -10 and -n = 15

⇒ m = 10 and n = -15

⇒ (m - n) = 10 - (-15) = 25.

Hence, Option 4 is the correct option.