Find average GDP according to continent in SQL -

Find average GDP according to continent in SQL -

i have 2 tables- economics (land_code, gdp) , continent (land_code, cont, percentage). need create query calculates average gross domestic product continent. in case country @ same time in several continents, should consider percentage of gross domestic product belongs continent. have understood if arab republic of egypt has gross domestic product of 100, 90 belongs africa , 10 asia, how can implement expression?

!!! done)

obviously,

select economics.land_code, economics.gdp * continent.percentage ...

sql