Fill in the boxes: `(square)/(15)=(-14)/(21)`

Answer

To solve the equation \(\frac{x}{15} = \frac{-14}{21}\), we will follow these steps:

### Step 1: Set up the equation
We start with the equation:
\[ \frac{x}{15} = \frac{-14}{21} \]

### Step 2: Cross-multiply
To eliminate the fractions, we will cross-multiply:
\[ x \cdot 21 = -14 \cdot 15 \]

### Step 3: Simplify the equation
Now we can simplify both sides:
\[ 21x = -14 \cdot 15 \]

### Step 4: Calculate \(-14 \cdot 15\)
We need to calculate \(-14 \cdot 15\):
\[ -14 \cdot 15 = -210 \]
So now we have:
\[ 21x = -210 \]

### Step 5: Solve for \(x\)
To find \(x\), we divide both sides by 21:
\[ x = \frac{-210}{21} \]

### Step 6: Simplify \(\frac{-210}{21}\)
Now we simplify \(\frac{-210}{21}\):
\[ x = -10 \]

### Final Result
Thus, the value of \(x\) is:
\[ x = -10 \]