The sum of -135 and 257 is larger.
Work Step by Step
When adding a negative number and a positive number, the sum has the sign of the number with the larger absolute value. Since 257 is larger than 135, the sum of -135 and 257 will be positive. The sum of 135 and -257 will be negative. Any positive number is greater than any negative number. Since the sum of -135 and 257 is the positive sum, it is the greater sum.