It is so very simple and quick to get the answer, especially since, if you need it, you can use the calculator that comes with your computer. But since you are obviously not able to do so, the answer is 690.
345 + 890 + 549 = 1784
55555555 + 345 = 55555900
325 + 345 = 670
345 + 67797808 = 67798153
345 + 435 = 780
200 + 345 = 545
2 + 345 = 347
345 + 253 = 598
345 + 890 = 1235
1 + 55 + 345 + 87 + 98 = 586
345 + 69 = 414
1 billion and 345