Answer:
-r + 9
Explanation:
Like terms are those with the same variable
Ex. Lets say we have 4a + 4b + 2a.
4a and 2a would be like terms as they share the same variable, the variable being a.
We have 4r - 6r + 9 + r
9 is by itself so we leave it as it is
The like terms would be 4r, -6r and r as they share r for a variable
So we simply combine ( add ) them together
4r + (-6r) + r = - r
We are left with - r + 9