#### Answer

1.259 + 5.312 + 1.7 $\approx$ 8

#### Work Step by Step

When rounding, if the subsequent digit is less than 5, you are to round down. If the subsequent digit is greater than or equal to five, you are to round up. If you round to the nearest ones digit in this question, 1.259 rounds down to 1 because the decimal value (0.259) is less than 0.5, 5.312 rounds down to 5 because the decimal value (0.312) is less than 0.5, and 1.7 rounds up to 2 because the decimal value (0.7) is greater than 0.5. The resulting calculation is:
1 + 5 + 2 = 8
Therefore, the sum of this equation is approximately 8.