21n+36n+7

I got 57n+7
my book has 57n+10
how'd they get 10??

also what this all about? how do I do it?
3x2'+4x-6
+2x2'-2x+5

the twos are a little one, slightly above the x

I don't know what you are supposed to do for the first one. Is that all the problem? or what are the directions?

For the second one, the small numbers slightly above the line are superscripts like this, X2 but those are so much trouble to write that we usually denote superscripts on these sites with a caret as in X^2. Anyway, the second equation can be simplified by combining like terms; that is, combine the X^2, the X and the numbers.
3X^2 and 2X^2 = 5X^2.
The 4X and -2X = 2X.
The -6 and +5 = -1. Therefore,
3X^2 + 4X -6 + 2X^2 -2X + 5 = 5X^2 + 2X -1
Check my work.

it says simplify
21n+36n+7

thank you for the second one.

It appears to me it should be 57n + 7 just as you have. I have no idea where the 10 comes from.