you combine -2y with -8y to get negative -10y. Then you combine 3 and 8.4 to get 11. Variables usually come first in equations, I don't think it matters, but you might want to put them first anyway.
I remember this from a long time ago but any number repeating that is less than nine is just put over 9, but as it goes up you put it over 99 and so on.
