751999-459•39+315:31=

Let's break down the expression step by step:

1. Calculate \( 459 \times 39 \): \[ 459 \times 39 = 17901 \]

2. Calculate \( 315 \div 31 \): \[ 315 \div 31 = 10.16129032 \quad (\text{approx. } 10.16) \]

3. Substitute the results back into the original expression: \[ 751999 - 17901 + 10.16 \]

4. Perform the subtraction: \[ 751999 - 17901 = 734098 \]

5. Finally, add the result of the division: \[ 734098 + 10.16 = 734108.16 \]

Therefore, the result of the expression \( 751999 - 459 \times 39 + 315 \div 31 \) is approximately \( 734108.16 \).