The problem tells you that a circle with radius 21 inches is painted in two colors. The two colors cover equal areas, so each color is half the area of the circle. You need to find half of the area of the circle. To do that, use the formula for the area of a circle, and then divide by 2.
[tex] A = \pi r^2 [/tex]
[tex] A = 3.14 \times 21~ inches \times 21~inches [/tex]
[tex] A = 1384.74~square ~inches [/tex]
Half the circle has area 1384.74 square inches / 2 = 692.37 square inches.
Answer: Each color covers 692.37 square inches.