Feild type is change as per the selection in combo box?

Now I create a combo box with two selection feild are Boy and girl.below that two text box one is boy age and another one is girl age to enter the data …when i select a boy form combo box.below the boy feild text box visible to user to enter the data another girl feild text box is invisible to the user ?How to Do in erpnext?

Check how Depends On works in ERPNext.

You can set value in the Depends On field from Customize Form.