Step 1: Find the relation between the side and height of the equilateral triangle.

             NOTE: If "h" is the height of the equilateral triangle and "a" its side, we have the relationship

             h = a * \frac{\sqrt{3}}{2}

             a = \frac {h*2}{\sqrt{3}}

Step 2: Find the side of the equilateral triangle by substitute the h value in the formula

               a = \frac {20*2}{\sqrt{3}}

               a = \frac{40}{\sqrt{3}}

Step 3: Find the area of the equilateral triangle when you know side

           Step 1: Set up a area formula of an equilateral triangle.

                NOTE: Equilateral triangle all sides are equal.

                           Area of equilateral triangle = \frac{\sqrt{3}}{4} a^2

           Step 2: Plug in the side (a) value in the area of the equilateral

            triangle formula

            EXAMPLE: Side a = 10 cm

                                            = \frac{\sqrt{3}}{4} a^2

                                            = \frac{\sqrt{3}}{4} (10)^2

            Step 3: Do Some calculations for the required area.

                      EXAMPLE = \frac{\sqrt{3}}{4} (100)

                                        = \sqrt{3}* 25

                                        = 25 \sqrt{3}