这个怎么写，求大神教一教

请教一下，这个不会写，真的好难啊，搞不懂怎算，这个到底是啥意思

参考这个：
http://www.kaotop.com/it/29860.html

#个税计算器
n=eval(input())
x=0
if n<0:
    print('error')
else:
    if 0<=n<=5000:
        x=0
    elif 0<n-5000<=3000:
        x=(n-5000)*0.03
    elif 3000<n-5000<=12000:
        x=(n-5000)*0.1-210
    elif 12000<n-5000<=25000:
        x=(n-5000)*0.2-1410
    elif 25000<n-5000<=35000:
        x=(n-5000)*0.25-2660
    elif 35000<n-5000<=55000:
        x=(n-5000)*0.3-4410
    elif 55000<n-5000<=80000:
        x=(n-5000)*0.35-7160
    elif 80000<n-5000:
        x=(n-5000)*0.45-15160
    y=n-x
    print('应缴税款{:.2f}元，实发工资{:.2f}元。'.format(x,y))

有帮助的话采纳一下哦！

sal1 = float(input())
a = 0
while True:

    if sal1 < 0:
        print("error")
        break
    elif sal1 <= 5000:
        a = 0
    sal = sal1-5000
    if sal <= 3000:
        a = sal*0.03
    elif sal <= 12000:
        a = sal*0.1 - 210
    elif sal <= 25000:
        a = sal*0.2 - 1410
    elif sal <= 35000:
        a = sal*0.25 - 2660
    elif sal <= 55000:
        a = sal*0.3 - 4410
    elif sal <= 80000:
        a = sal*0.35 - 7160
    else:
        a = sal*0.45 - 15160
    sal = sal1-a
    print("应缴税款{:.2f},实发工资为{:.2f}".format(a,sal))
    break