Final answer:
The code will print 'I am13 years old'.
Step-by-step explanation:
The code segment given is as follows:
String str = "I am";
str += 10 + 3;
String age = "years old";
System.out.println(str + age);
When this code is executed, it will print I am13 years old.
The reason for this is the concatenation and arithmetic operations happening in the code. The variable 'str' initially stores the string 'I am'. Then, the '+=' operator is used to concatenate the value of 'str' with the result of the expression '10 + 3', which is 13. Finally, the 'println' statement prints the concatenated string 'I am13 years old' to the console.