I am struggling with the following task:

For the production of ? = 10kg/h of salve with 5% of substance A and 2% of substance B are the following basics available:

> Base 1: 20% of substance A; 1% of substance B in salve base

> Base 2: 5% of substance A; 10% of substance B in salve base

> Base 3: 100%

What massflow do I need for each base to produce the salve.
I am thinking about using a equation system but I just don't know where to start and how to transate the task into an equation...