In ΔABC, DE || BC so that AD = (7x — 4) cm, AE = (5x — 2) cm, DB = (3x + 4) cm and EC = 3x cm. Then, we have
By Basic Proportionality Theorem:
If a line is drawn parallel to one side of a triangle to intersect the other two sides in distinct points, the other two sides are divided in the same ratio.
= 
3x (7x — 4) = (5x — 2) (3x + 4)
21 x2 – 12x = 15x2 + 14x – 8
6 x2 – 26x + 8 = 0
3 x2 – 13x + 4 = 0
3 x2 – 12x – x + 4 = 0
3x(x - 4) – 1(x - 4) = 0
X = 1/3, 4
Since x cannot be 1/3 so x = 4
25