Awater canal has a rectangular cross section 3 meters wide and 2 meters deep. how much water is contained in a 30-meter length of the canal? how much water does it hold after 60% of the water has evaporated

Basically you are finding the volume of a rectangular prism of 3 by 2 meters cross section and 30 meters length.  Volume = (3 m)(2 m)(30 m) = 180 cubic meters.

If 60% of the water has evaporated, 40% is left.  Find 40% of 180 cubic meters to answer the 2nd part of this question.