For this case, we have that by definition, the area of a triangle is given by:
[tex]A = \frac {b * h} {2}[/tex]
where:
b: It's the base
h: It's the height
In this case we have:
[tex]b = 21 \ ft\\h = 6 \ ft[/tex]
Substituting:
[tex]A = \frac {21 * 6} {2}\\A = 63 \ ft ^ 2[/tex]
Answer:
[tex]63 \ ft ^ 2[/tex]
