A petrol tank that is 1/2 full has 10 gallons petrol removed. The tank is then 1/10 full. What is the capacity, in gallons of the tank?

Question: A petrol tank that is 1/2 full has 10 gallons petrol removed. The tank is then 1/10 full. What is the capacity, in gallons of the tank?

Solution:
Let,
The capacity of the tank in gallons is x gallons.

ATQ,
⇒ (x/2) - 10 = x/10
⇒ (x - 20)/2 = x/10
⇒ 10(x - 20) = 2x
⇒ 10x - 200 = 2x
⇒ 10x - 2x = 200
⇒ 8x = 200
∴ x = 200/8 = 25 gallons