LA=3.5; AY=7
LW=?
LW=LA+AW
AW=?
Let's analyze triangles LAY and YAW
1) Triangle LAY
Angle LAY is 90°
Suppose Angle ALY is x
The angle LYA is the complement of x, for example y:
x+y=90°→y=90°-x
2) Triangle YAW
Angle AYW is the complement of angle LAY (y), then the angle AYW must be equal to x.
Angle YAW is 90°, because the angle LAY is 90°
The triangles LAY and YAW are similars, because they have to congruent angles:
Angle LAY = 90° = Angle YAW
Angle ALY = x = Angle AYW
Then the sides of triangles LAY and YAW must be proportionals:
AW/AY=AY/LA
Replacing the known values:
AW/7=7/3.5
AW/7=2
Solving for AW. Multiplying both sides of the equation by 7:
7(AW/7)=7(2)
AW=14
Now:
LW=LA+AW
LW=3.5+14
LW=17.5
Answer: LW=17.5 units