you would divide 100 by 4 first because according to PEMDAS (If you learned it already), you would have to go from left to right, and multiplication/division comes before addition/subtraction--so you do that math first--and you would get 25. Then you would do the multiplication because, like I said from before, Multiplication/division comes before addition/subtraction, so you then multiply 25 by 3 to get 75. After this, you do the math from the left to the right, and adding -9 to 75 is the same as 75 minus 9, so you would get 66, and that is your answer.