John took all his money from his savings account. He spent $72 on a radio and two thirds of what was left on presents for his friends. John then put five twelfths of his remaining money into a checking account and donated the $140 that was left to charity. How much money did john originally have in his savings account

Let us assume amount of money John originally have in his savings account = $x

Money spent on a radio = $72.

Reamining money = x-72.

Money spent on presents for his friends = Two third of remaining money = 2/3 (x-72).

(Because 1 - 2/3 = 1/1 - 2/3 = 1/3)

Reamining money = 1/3 (x-72).

Five twelfths of his remaining money into a checking account = 5/12 * 1/3 (x-72).

(becasue 1 - 5/12 = 1/1 - 5/12 = 7/12)

Reamining money = 7/12 * 1/3 * (x - 72).

Final remaining money = 7/12 * 1/3 * (x - 72) and that is equal to the money donated to charity.

We can setup an equation now.

7/12 * 1/3 * (x - 72) = 140.

7/36 (x-72) = 140.

Multiplying both sides by 36.

36 * 7/36 (x-72) = 140 * 36

7 (x-72) = 5040.

Dividing both sides by 7, we get

7 (x-72) / 7 = 5040/7

x-72 = 720

Adding 72 on both side, we get

x-72+72 = 720+72.

x = 792.

Therefore, john originally have $792 in his savings account.