Total time = upstream time + downstream time
he rowed the same distance both ways.
upstream time = D/4
downstream time = D/6
total time = D/4 + D/6 = 3D/12 + 2D/12 = 5D/12 = 3 hours
D = 3*12/5 = 36/5 or 7.2 miles
where D is the one-way distance. The total distance he rowed is 2*D = 72/5 or 14.4 miles
Area of the entire rectangle 
Solution:
Area of the blue box = length × width

Area of the blue box 
Area of the pink box = length × width

Area of the pink box 
Area of the green box = length × width

Area of the green box 
Area of the orange box = length × width

Area of the orange box = 24
Total area of the rectangle 

Area of the entire rectangle
The answer to your question is A
Tree 3 diagram is the answer