Hi there!
To solve this problem, we need to divide 67.8 by 6 to find the amount of hours each day.
67.8 / 6 = 11.3
You worked 11.3 hours each day.
Hope this helps!
This document has the answer
The 4 litres of red has to be 2 parts of the mixture, so each part will be 2 litres. Therefore 3 parts of cream will be 6 litres and the one part of blue will be 2 litres.
You just have to look at the form of the equations
The only linear equations would be y = mx + b and Ax + By = C