I'll give you a hint. You had to used pemdas stands for: p-parenthesis, e-exponents, m-multiply, d-divide, a-add, and s-subtracting.
First you had to calculate with parenthesis first.
[tex](6-4)=2-9[/tex]
Then you add and subtract from left to right.
[tex]2-9=-7[/tex]
Final answer [tex]\boxed{=-7}[/tex]
Hope this helps!
And thank you for posting your question at here on brainly, and have a great day.
-Charlie