In the given figure, if yx=5 and zx=4, then the value of x∘ is
(a) 8∘
(b) 18∘
(c) 12∘
(d) 15∘
In the given figure, we have x∘,y∘ and z∘ forming a linear pair, therefore these angles must be supplementary.
That is,
x∘+y∘+z∘=180∘ ---(i)
It is given that, yx=5
⇒y=5x ---(ii)
and, zx=4
⇒z=4x ---(iii)
Substituting (ii) and (iii) in (i), we get:
x∘+y∘+z∘=180∘
⇒x∘+5x∘+4x∘=180∘
⇒10x∘=180∘
⇒x∘=180∘10
⇒x∘=18∘
Hence, the correct choice is (b).