<em><u>for 20</u></em>: let's first say the equation to figure out if it is a right triangle (the pythagorean theorem). so a^2 + b^2 = c^2 -> 2^2 + 2^2 =3^2 -> 4+4=9 does not equal out so 20 is not a right triangle.
<em><u>for</u></em><em><u> </u></em><em><u>2</u></em><em><u>7</u></em><em><u>:</u></em> the equation for area is (height×base)/2 -> (2×4)/2 -> area = 4
<em><u>for</u></em><em><u> </u></em><em><u>2</u></em><em><u>9</u></em><em><u>:</u></em> so let's find the circumference first. the equation is 2× pi × r -> 2× pi × 5 -> circumference = 10pi or about 31.42.
so now we can find the area of the circle. the equation is pi × r^2 -> pi × 5^2 -> area of circle= 25pi or about 78.54