Order of operations.
Parentheses
Exponents
Multiplication
Division
Addition
Subtraction
We must do parenthesis first.
72 - 13 = 59
We have now
20 + 15(59) - 67 + 6
20 + 885 - 67 + 6
905 - 67 + 6
905 - 61
844
Hope this helped! If you have any questions then leave a comment.