What's the diameter of a circle suppose to be if What's the diameter of a circle suppose to be, if the area is suppose to be same as equilateral of triangle with the circumference of 3meters?

Answer: 74cm

No idea how I am suppose to start.
The area of a triangle is $\frac12 \cdot b \cdot h$ We know that each side of the triangle is one meter because it is an equilateral triangle, and each angle is 60°. A height must connect a vertex to the base so that it is perpendicular to the base. That means that the height bisects the vertex angle, so you have a 30-60-90 triangle. The sides of a 30-60-90 triangle are in a ratio of $x:x\sqrt3:2x$ with x opposite the 30° angle, $x\sqrt3$ opposite the 60° angle and 2x opposite the right angle, so the height is $\frac{2}{\sqrt3}$ times the hypotenuse, or 1.15 meters. You can then find the area of the triangle by plugging the height and base into the area formula. Next, we must find the radius of the circle using the area. The area of a circle is expressed as $A=\pi \cdot r^2$ so we can substitute the area of the triangle for A and solve for r. It should be $\sqrt{\frac{A}{\pi}}$. Multiply that by 2 to get the diameter in meters and convert it to centimeters by dividing be 100.
Equate the area of the circle and the area of the equilateral triangle. You can easily obtain the radius of the circle from there and hence, the diameter.