Explain Plan Question

In my sql below, what determines the order in which tables are processed?

Is it the order in the FROM clause?

Or the order of the WHERE clause?

Thanks,

P

SELECT xa.address_1
,xa.address_2
,xa.address_3
,xa.address_4
,xa.city
,xa.county_code
,xa.county_desc
,xa.province
,xa.state_code
,xa.state_desc
,xa.zipcode
,xa.zip_plus_four
,xa.country_code
,xa.address_type_code
,xa.country_desc
,xp.area_code
,xp.phone_number
,xp.phone_extension
,decode(nvl(xp.area_code,-1),xp.area_code,'('||xp.area_code||') ','')||
decode(nvl(xp.phone_number,-1),xp.phone_number,substr(xp.phone_number,1,3)||'-'||substr(xp.phone_number,4,7),'') phone_f
,xf.area_code fax_area
,xf.phone_number fax
,decode(nvl(xf.area_code,-1),xf.area_code,'('||xf.area_code||') ','')||
decode(nvl(xf.phone_number,-1),xf.phone_number,substr(xf.phone_number,1,3)||'-'||substr(xf.phone_number,4,7),'') fax_f
FROM xt_address xa
,xt_phone xp
,xt_phone xf
WHERE xa.request_id = p_request_id
AND xa.source_table_name = 'RISK'
AND xa.primary_address_b <> 'Y'
AND xa.effective_to_date = '01-JAN-3000'
AND xp.request_id(+) = xa.request_id
AND xp.source_record_fk(+) = xa.source_record_fk
AND xp.source_table_name(+) = 'RISK'
AND xp.phone_number_type_code(+) NOT LIKE '%FAX%'
AND xp.effective_to_date(+) = '01-JAN-3000'
-- AND xp.primary_number_b(+) = 'Y'
AND xf.request_id(+) = xa.request_id
AND xf.source_record_fk(+) = xa.source_record_fk
AND xf.source_table_name(+) = 'RISK'
AND xf.phone_number_type_code(+) LIKE '%FAX%'
AND xf.effective_to_date(+) = '01-JAN-3000'
AND ROWNUM = 1;