Show me the steps to solve in sql These are the columns from the customer$\_$spending table

sale$\_$date, date

sale$\_$year, integer

sale$\_$month, character varying $(255)$

age, integer

gender, character

country, character varying $(255)$

state, character varying $(255)$

category, character varying $(255)$

sub$\_$category, character varying $(255)$

quantity, integer

unit$\_$cost$,$ numeric $(6,2)$

unit$\_$price, numeric $(10,6)$

cost$,$ integer

revenue, integer

in sql Write a query that returns a list of countries where more than $900$ transactions were made by customers between the ages of $18-25($inclusive$).$