+----------------------------------+
|+---------+ +--------------------+|
||  33%    | |  width: normally   ||
||         | |  66%; otherwise    ||
|| min:    | |  min-width:600px   ||
||   300px | |                    ||
|+---------+ +--------------------+|
+----------------------------------+
|<|                 |=|          |>|
+----------------------------------+

+----------------------------------+
|+---------+                       |
||         |                       |
||         | +--------------------+|
||         | |                    ||
||         | |                    ||   <----  I get something like this
|+---------+ +--------------------+|
+----------------------------------+
|<|                 |=|          |>|
+----------------------------------+

+----------------------------------+
|+---------+ +--------------------+|
||         | |                    ||
||         | |                    ||
||         | +--------------------+|
||         |                       |
|+---------+                       |
+----------------------------------+
|<|                 |=|          |>|
+----------------------------------+

.firstDiv{
    display:inline-block;
    min-width:300px;
    width:33%;
    background-color:red;
    white-space:normal;
}
.secondDiv{
    display:inline-block;
    min-width:600px;
    width:66%;
    background-color:orange;
    white-space:normal;
}

.parent{
    overflow-x:scroll;
    white-space:nowrap;
    background-color:blue;
    height:400px;
    width:100%;
    top:0;
}