Follow PEMDAS.
Parenthesis
Exponents
Multiplication & Division
Addition & Subtraction
Alright, do multiplication first, then division. Then, do subtraction then addition.

Hope this helped!
When you multiply a same number but with different powers, you can simply add the powers together. So, in your question, add the powers -1 and -7 together.
7^(-1) x 7^(-7) = 7^(-8)
When you divide a same number but with different powers, you subtract the power at the top with the power from the denominator. So, -8 - (-7) = -1.
7^(-8) / 7^(-7) = 7^(-1)
So your answer would be 7^(-1).
Hopefully my explanation was clear?
Answer:
3x+5=5x-9(llgram oppositesides are equal)
3x-5x= -9-5
-2x=-14
x= -14/-2
x=7