Primary 2 Math Question

I'm afraid I don't understand your notation.

Do you mean:
4+8+9+2+10+3 = 6+7+8+6+?+4

If so, then ? =5 .

Thanks,I think I have figured out the answer because of your method.
4+8+9+2=25
9+2+6+8=25
25-10-3-4=8

Thank you. However, I still don't quite understand what | means, whether it is a
plus: +
minus: -
division: ÷, sometimes /
multiplication: X, sometimes *
Is it common to use the | symbol in math in your country, or is this the result of the differences in languages that computer keyboards come in?

Quote Loh Jane

I believe that 4+8+9+2= 23, not 25.

Sorry,should be 4+8+6+7=25

And that's the problem. Without knowing what it means you're left with guesswork. I remember modern maths when I was at school, things like matrices left my parents cold.

This could be a simple arithmetical problem or it could be something else you're just not familiar with because you, (and I,) weren't taught it. It may have something to do with coding or sequencing or even algorithms. The best thing the OP could do is talk to her niece's teacher.