20/(x+12) + (x+2)/(x+32) =1
分母不为零,所以x+12≠0,x+32≠0,即x≠-12,x≠-32
两边同乘以(x+12)(x+32)：
20(x+32) + (x+2)(x+12) = (x+12)(x+32)
20(x+32) + (x+2)(x+12) - (x+12)(x+32) = 0
20(x+32) + (x+12)（x+2-x-32) = 0
20(x+32) -30 (x+12) = 0
20x+640-30x-360 = 0
-10x+280=0
x = 28