Help with a few math questions

I need help with a few math questions i need to do to.

I need to simplify
3x-2x² + 4x +7x²

and simplify
3(4x-7)

i also have to solve

2x+3=19

Any help would be appreciated :)

1. (3x+4x)+(-2x² +7x² )
7x+5x²
5x² +7x

2.12x-21

3. 2x+3=19
2x=16
x=8

For the person below me: The problem is 2x+3=19, not 2x+13=19 :)
For the person 2 below me: You can still simplify the first problem to 5x² +7x :)

For the 2x+13=19 one:)

2x+13=19
take 13 over the other side and it'll become negative

2x=19-13
2x=6
take the 2 over the otherside and it'll become dived as it was times before

x=6/2
how many times dies 2 go into 6...
x=3 Thats the answer:)

3x - 2x² + 4x + 7x² = (7*x^2 - 2*x^2) + (3*x + 4*x) = 5*x^2 + 7*x = x*(5*x + 7)

3*(4*x - 7) = 12*x - 21

2*x + 3 = 19

2*x = 19 - 3

2*x = 16

x = 16/2

x = 8