In the figure at the right, △ABC ~ △ADE.
( The picture and dimensions of the triangle is here: 
)
a. Substitute values from the diagram into the following proportion: AD/AB = DE/BC
(Hint : AB = AD + DB).
AD/AB = DE/BC
8/(8+x) = 5/7
b. Solve the proportion for x.
8/(8+x) = 5/7
8(7) = 5(8 + x)
56 = 40 + 8x
8x = 56 - 40
x = 16/5 ≈ 3.2 ins
c. Find the length of AB.
AB= AD + DB AB = 8 + x AB = 8 + 3.2
AB = 11.2 ins
d. What is the area of △ABC?
Area of Triangle = ½ Base x Hieght
Area of Triangle = ½(11.2 x 7)
Ara of Triangle = 39.2 ins²
Thanks in advanced!