DD7 in 2nd grade this year had problems like the one Wren quoted but they were from a 3rd grade textbook (her school teaches ahead).
The issue with multiple solutions that I could see is that (no offense to elem. teachers) but some of them may take the answer out of the book and unless the book notes multiple solutions I could see my kid coming home and saying her teacher told her she was wrong at which point I would end up having to conference with them via email about multiple solutions in some nice way. I'm sure I would end up being tactless but sometimes teachers will go strictly by the book if they aren't comfortable with a subject. Kids at that age are likely to believe their teacher that they were wrong even when they did it correctly (just different)
FWIW based on what I saw with my older daughter, My guess is that they are getting the second graders ready to deal with the guess and check problems in 3rd grade. These are really easily solved by setting up systems of equations via algebra. But they show elem kids how to make a table and guess and iterate. Apparently, it can give them number sense in that they need to figure out which way to adjust their guesses. I worry it will put some kids off algebra later if they know they can guess.
