In fact, we won't do these questions either. It depends on what you have learned. At different stages, the same problem needs different solutions. Do you want me to guess?

50+42= Should we bring 42=40+2 and 50 into 50+40 and then +2?

5+42= Should we bring 42=40+2 and 5 into 5+2 and then +40?

I only remember doing similar topics in primary school. I don't know if I guessed correctly. I should study hard and look at the examples. The primary school curriculum is the same.

But now the topic is very difficult.