Let x be the amount of paint needed to cover her entire wall
she uses two and one half gallons of paint to cover one eighth of her wall
That is;
2 1/2 paints = 1/8 of wall
X = 1 wall
cross multiply
1/8 x X = 2 1/2 x 1
X/8 = 2 1/2
X/8 = 5/2
cross-multiply
2X = 40
Divide both-side of the equation by 2
X = 20
Hence, she needs 20 gallons of paint to cover her entire wall.
