4x+20=5x-10
两边同时加10,然后两边同时减4x
得到x=30
x=30
4x+5×4=5x-5×2
4x+20=5x-10
4x+20+10=5x (左右两边同时+10)
4x+30=5x
30=x (左右两边同时-4x)
x=30
4x+20=5x-10
x=30
4x+5*4=5x-5*2
4x+20=5x-10
4x-5x=-10-20
-x=-30
x=30
4x+5*4=5x-5*2
4x-5x=-5*2-5*4
-x=-10-20
-x=-30
x=30