



 
Yinna, You know that the area A of a triangle is given by
where b is the base length and h is the height. Thus for your triangle you know that
You are told that for this triangle the "height is 2 times the base", that is h = 2 × b. In the equation above substitute 2 × b for h. This gives you an equation in b alone. Solve it for b. I hope this helps,  


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