If two gallons of paint covers 800 square feet, 'x' gallons of paints will cover 1200square feet room where x is the number of gallons needed to paint the 1200 square feet room.
Mathematically,
2 gallons = 800sq.ft
x gallons = 1,200sq.ft
x × 800 = 2 × 1200
x = 2 × 1200/800
x = 3 gallons
Therefore Leah will need 3gallons of paint for 1200sq.ft room
