PEMDAS. You do parentheses first, then exponents, the multiplication and division, the adding subtracting.
55 + a (y x 6) - 9
So you distribute a to y and 6 — 55 + ay x 6a -9
Subtract 9 from 55 — 46 + ay x 6a
Multiply ay and 6a (because they both have a) __ 46 + 6ay
That’s your answer.
I hope this helped!