Step 1: Inspect the given figure and change the figure according to the given hints in the question.

NOTE :Figure above shows that the centers of the circles make an

equilateral triangle of side 2r where r = 15 (given) is the radius of one circle.

Step 2: Set up a formula to calculate the shaded region

NOTE: The area of the red shape = area of the equilateral triangle - areas

of three congruent sectors (each sector has 60° angle)

Step 3: Find the area of the equilateral triangle

FORMULA: a^2 \frac{\sqrt{3}}{4}

= (2r)^2 \frac{\sqrt{3}}{4}

= (30)^2 \frac{\sqrt{3}}{4}

Step 4: Calculate the areas of three congruent sectors

NOTE: Areas of three congruent sectors = 3 × area of one sector

Area of the sector = \frac{\theta}{360} * \pi r^2

= \frac{60}{360} \pi (15)^2

= \frac{1}{6} 15^2 \pi

Areas of three congruent sectors = 3 * \frac{1}{6} 15^2 \pi

Step 5: Find the shaded region in the figure

The area of the red shape = (30)^2 \frac{\sqrt{3}}{4} - \frac{15^2 \pi}{2}

Step 6: Simplify the equation

NOTE: (30)^2 \frac{\sqrt{3}}{4} - \frac{15^2 \pi}{2}

= [(900 * 0.433 ) - (112.5 * 3.14)

= 389.711 - 353.25

= 36.46 unit^2