方程x+1/0.2 - 3x-1/0.4=1

题目

方程x+1/0.2 - 3x-1/0.4=1
答案是13/5

答案

x + 10/2 - 3x - 10/4 = 1
(x-3x) + 5 - 5/2 = 1
-2x = 1 - 5 + 5/2
2x = -(-1/2+10/2-5/2)
2x = (1-10+5)/2
x = -1
.