Whats 6[4x (72-63) : 3]

The answer is 72

you first start by doing whats in the parenthesis: 72-63. that equals 9. then do the brackets [4 (9) / 3] do this from left to right 4x9=36. 36/3 = 12 last do 6x12 that equals 72 which is the most simplified version