<PRE><B>Question 579844</B>
Area of triangle = 1/2 * base * height

15= 1/2 * (x-5)(2x+1)

multiply by 2
30 = (x-5)(2x+1)

30= x(2x+1)-5(2x+1)

30=2x^2+x-10x-5

30=2x^2-9x-5

add -30
0= 2x^2-9x-35

2x^2-9x-35=0

2x^2-14x+5x-35=0

2x(x-7)+5(x-7)=0

(x-7)(x+5)=0

x=7 OR -5

x=7 since the lengths cannot be negative.</PRE>