string + number = concatenated string
number + number = the sum of both numbers
string - number = the difference between (coerced string) and the number
explanation:
If one or both operands is string, then the plus is considered as string concatenation operator rather than adding numbers.
the minus operator always try to convert both operands to numbers.
so:
"" + 1 + 10 + 2 = (string) "1102"
"1102" - 5 = (number) 1097
1097 + "8" = (string) "10798"
