You can display the value from your PL/SQL block with the DBMS_OUTPUT.PUT_LINE package procedure.
DBMS_OUTPUT is an Oracle-supplied package, and PUT_LINE is a procedure within that package.

Within a PL/SQL block, you can reference DBMS_OUTPUT.PUT_LINE and, in parentheses, provide the information you want to print to the screen. The information you put in the parentheses must be a string value.

SET SERVEROUTPUT ON
DECLARE
BEGIN 
DBMS_OUTPUT.PUT_LINE (‘string value that needs to be
displayed on the screen’)
END;

The declaration of a host variable and referencing it within your PL/SQL block has been discussed.
Take a look at the following link to understand exactly how to accept the price of a pet and display the price on the screen.
Values Sql Plus Screen

Click the Exercise link below to use bind and host variables in a simulation.
Oracle Naming Conventions Exercise