how to solve 3 table and group same id?

```
   t1
----------
Id   a
1   100
1   600
2   800

  t2
----------
Id    b
1    600
2    700
3    400

  t3
----------
Id    c
2    400
3    800
4    100 

```

i want result like this:

```
Id     a        b      c 
------------------------------
 1    700      600   
 2    800      700    400      
 3             400    800
 4                    100

```

Same id group by