Answer:
To paint the room with dimension 30 ft by 50 ft by 50 ft is 26.67 gallon    
Step-by-step explanation:
Given as :
The Length of wall = L = 50 ft
The width of wall   = W = 30 ft
The height of wall  = H = 50 ft 
Each gallon of paints should cover 300 sq feet
Let the amount o gallon required to paint the room = x 
SO, Area of four wall = 2 × ( L + W ) × H 
Or, Area of four wall = 2 × ( 50 + 30 ) × 50
Or, Area of four wall = 2 × ( 80 ) × 50
SO, Area of four wall = 8000  ft² 
∵ To paint 300 sq ft the amount of paint required = 1 gallon 
∴ To paint 8000 sq ft the amount of paint required = 26.67 gallon 
Hence ,to paint the room with dimension 30 ft by 50 ft by 50 ft is 26.67 gallon      answer