450:(25+5•x)=15

To solve the equation \( 450 : (25 + 5 \cdot x) = 15 \), we can follow these steps:

1. Rewrite the division as a fraction: \[ \frac{450}{25 + 5x} = 15 \]

2. Cross-multiply to eliminate the fraction: \[ 450 = 15 \cdot (25 + 5x) \]

3. Distribute \( 15 \) on the right side: \[ 450 = 375 + 75x \]

4. Subtract \( 375 \) from both sides: \[ 450 - 375 = 75x \] \[ 75 = 75x \]

5. Divide both sides by \( 75 \): \[ x = 1 \]

Thus, the solution is \( x = 1 \).