Solve this... if you can

Hi !
I don't speak very english. :(
1) 3x = 30
30 ÷ 3 = 10
2) 10 + 2x = 12
12 - 10 = 2
2 ÷ 2 = 1
3) 2x + 1 = 15
15 - 1 = 14
14 ÷ 2 = 7
4) 10 × 1 + 7
10 + 7 = 17
Good afternoon ! :)