We can get: minuend = subtraction+difference =360÷2= 180.
180 ÷ (1+2+1) = 45 This is subtraction.
45×( 1+2)= 135 This is the difference.
The error is twice that of difference or subtraction, that is, the difference is three times that of subtraction, so we use180 ÷ (1+2+1).
Answer: The difference should be 135.