What does 3×+4×+5× equal by showing work. yes im a teacger

12x cuz 3+4+5=12 and you multiply it by the veritable.

Since they all have the same variable you can combine them all and it will equal 12x
If it didn't have the same variable then you wouldn't combine them and if one of them has no variable at all then the ones that do have a variable you do combine.

Example:
12x + 5p + 2
= 5p + 12x +2
Because p comes before x and 2 doesn't have a variable and none of them share the same variable

Other Example:
2x + 10x + 3
= 12x + 3
Because 10 and 2 have the same variable you do combine them and then 3 doesn't match so it stays alone

Overall the ANSWER IS:
= 12x

Sorry I wrote a lot, but it's just some tips