You can
put this solution on YOUR website!Let x=base so area of triangle in this instance is

multipy both sides by 2

subtract 30 from both sides to get Quadratic

which factors to
(x-5)(x+6)=0
x-5=0
x=5
x+6=0
x=-6
so obviously your answer is x=5 centimeters(length of base)
Pete