(1) If x=2 10, the electricity fee is 2 10*0.52= 109.2 (yuan) less than 138.84 yuan.

So x>2 10

Push down (sorry for typing, hehe) 2 10

So the equation (0.52+0.05) (x-210)+109.2 =138.84.

The solution is x=262.

(2) If

If 109.2

If 189

I don't know how to ask questions about children's shoes