Deriving addition and subtraction facts by using given calculations

Maths

What's the same? What's different? 364 + 302 = 666 and 374 + 302 = 676

What's the same? What's different? 764 - 204 = 560 and 754 - 204 = 550

What's the same? What's different? 3672 + 1474 = 5146 and 3972 + 1474 = 5446

If... 362 + 205 = 567 then... 262 + 205 = ?

If... 751 - 303 = 448 then... 741 - 303 = ?

What's the missing part in the following equation: 220 + ___ = 550

What's the missing part in the following equation: 110 + ___ = 660

Here are three derived facts, based on the fact 3 + 5 = 8. Which is incorrect?