My 2nd grader with his math homework and came across this. i don't know common core but i can find the sum "the old fashioned way" which is not how his teacher wants him to solve this one. can you me understand this?

raul used this method to find the sum 427 + 316.
427
+316

700
30
+ 13

743
describe how raul solves addition problems.

*note: i know this question was asked and answered in archives but the answer to how to solve this is still baffling me.*

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