數學題~~~~~~~~~~~~Help !!!!!!!

1.
4(x-4) = 2x-4
4x-16 = 2x-4
2x = 12
x = 6

2.
6(x+3) = 2(6x+3)
3(x+3) = 6x+3
3x+9 = 6x+3
6 = 3x
x = 2

3.你是否打錯題目?

4.
設該3個連續整數是 x,x+1,x+2
x+(x+1)+(x+2) = 45
3x+3 = 45
3x = 15
x = 5
所以該3個連續整數是5,6,7

5.
設￥50紙幣的數目為x
50x+20(x+4) = 360
50x+20x+80 = 360
70x = 280
x=4
所以￥20紙幣的數目是8

第四題錯丫！！！
５＋６＋７點會＝４５！！！
答案應該係１４，１５，１６！！！