Question

0.4y^2 + 0.6y^2-0.2y^2

Answer 1

I believe that because they are all y^2 then you can view it as if y^2 isn't even there
so .4 +.6 -.2 =
and just remember to add on y^2 to your answer

Answer 2

they all having the same literal coefficient which is y^2 therefor they are all like terms and you can add or subtract them .. so the answer is 0.8y^2