SQL Query to SUM data from 3 different tables

I have 3 2005 SQL tables, an order table, quote table and invoice table. Structured like this:

SO Table

Rep Code SO Amount SO Date

1         100     1/2/2015
2         50      2/15/2015
3         20      2/20/2015
2         50      2/20/2015
1         85      2/20/2015

SQ Table

Rep Code SQ Amount SQ Date

1        50        2/2/2015
2        14        2/18/2015
3        67        2/19/2015
1        96        2/20/2015
2        54        2/20/2015

INV Table

Rep Code INV Amount INV Date

1         654      2/2/2015
2         312      2/18/2015
3         54       2/19/2015
1         6        2/20/2015
3        48        2/20/2015

What I want to do is write a query which will sum up each amount by rep code, so it would look something like this:

Rep Code SO Total SQ Total Inv Total

1        185      146      660
2        100       68      312
3        20        67      102

I would also like it to only pull the totals if the appropriate date for each one is lets say in the last week. (So Today -7)

Let me know if this needs any clarification.