Refer to the attached for step by step explaination.
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<h2>what is the equation so i could answer it </h2>
Area=1/2bh
h=altitude
b=legnth of base
b is 3 times h
b=3h
divide by 3
b/3=h
area=1/2bh
subsitute b/3 for h
54=1/2(b)(b/3)
multiply bothsides by 2/1
108=b(b/3)
108=(b^2)/3
multipy both sides by 3
324=b^2
square root boh sides
18=b
legnth of base=18