So we have (9a + 5) x (6a - 5)
So we can expand one bracket to get:
= {9a x (6a - 5)} + {5 x (6a - 5)}
= {54a^2 - 45a} + {30a - 25}
Now its simple, we open all the brackets and do simple addition of like terms:
= 54a^2 - 45a + 30a - 25
= 54a^2 - 15a - 25
And that’s the final answer.