Simplify : `(15x-4y)+(15x+4y+3)-45x+12y`.

Answer

To simplify the expression `(15x - 4y) + (15x + 4y + 3) - 45x + 12y`, we can follow these steps:

### Step 1: Remove the brackets
We start by rewriting the expression without the brackets:
\[ 15x - 4y + 15x + 4y + 3 - 45x + 12y \]

### Step 2: Combine like terms
Next, we group the like terms together. The like terms are the terms with \(x\) and the terms with \(y\), as well as the constant term.
- Combine the \(x\) terms:
\[ 15x + 15x - 45x = 30x - 45x = -15x \]
- Combine the \(y\) terms:
\[ -4y + 4y + 12y = 0 + 12y = 12y \]
- The constant term remains as it is:
\[ + 3 \]

### Step 3: Write the simplified expression
Now we can write the simplified expression by combining all the results from the previous step:
\[ -15x + 12y + 3 \]

### Final Answer
Thus, the simplified expression is:
\[ -15x + 12y + 3 \]

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