WILL MEDAL What is the value of x
a)4.2 b) 8.4 c)12 d) 18
http://www.thelearningodyssey.com/Assess/DPT/QIEImagesStorage/AQ13G/AQ13GE_GE534_09_stem1_1.jpg

Question

WILL MEDAL What is the value of x
a)4.2 b) 8.4 c)12 d) 18
http://www.thelearningodyssey.com/Assess/DPT/QIEImagesStorage/AQ13G/AQ13GE_GE534_09_stem1_1.jpg

danjs · Answer

the two triangles are similar, because of the parallel lines, you can show that all 3 angles are the same for both triangles

danjs · Answer

15 is to 2x-9 as 20 is to x+2

danjs · Answer

$$\frac{ 15 }{ 2x+9 }=\frac{ 20 }{ x+2 }$$

danjs · Answer

you see how i got that?

danjs · Answer

2 pairs of alternate interior angles are congruent, and a vertical angle pair, the triangles are similar

anonymous · Answer

Yeah but i still have no idea how to solve it. I know you cross multiply but...

danjs · Answer

yeah you can do the cross multiply thing... 

15(x + 2) = 20(2x + 9)

danjs · Answer

I copied from the diagram wrong, it is (2x - 9) not plus 9

danjs · Answer

15(x + 2) = 20(2x - 9)

danjs · Answer

distributing, 

15x + 30 = 40x - 180

danjs · Answer

take away 15x both sides

30 = 25x - 180

danjs · Answer

add 180 

210 = 25x

anonymous · Answer

got the answer thankya

danjs · Answer

cool, welcome