Answer:
39 + 3
42
393
Explanation:
In this line System.out.println("39 + 3"), the quotation marks are used to delimit a string, then when printed in the console the string is printed as-is.
In the next line: System.out.println(39 + 3), without the quotation marks, the 39+3 is treated as a normal addition and prints the result of the operation.
In the last line printed with the code System.out.println("39" + 3,; the symbol + is used to concatenate the string 39 with the number 3, since the string has no spaces they are printed together.