7x+9y-9(7x-8y+5z)= help me I do not know what to do.
To simplify the given expression, you can start by distributing the -9 across the terms inside the parentheses.
-9(7x - 8y + 5z) can be expanded as -9 * 7x + (-9) * (-8y) + (-9) * 5z.
This gives us -63x + 72y - 45z.
Now, you can rewrite the expression as:
7x + 9y - 63x + 72y - 45z.
Combine like terms:
(7x - 63x) + (9y + 72y) - 45z.
This simplifies to:
-56x + 81y - 45z.
So, the simplified form of 7x + 9y - 9(7x - 8y + 5z) is -56x + 81y - 45z.