Here triangles CMX and CDS are similar. SO we use the ratio rule of similar triangles which states that the ratio of the corresponding sides are in same proportion . That is
[tex] \frac{SM}{XD}=\frac{CS}{CX} [/tex]
Let SX=x
[tex] \frac{7}{9} = \frac{15}{15+x} [/tex]
Doing cross multiplication
7(15+x) = 9*15
Distributing 7 on 15 +x ,
105 +7x = 135
Subtracting 105
7x=30
Dividing both sides by 7
x= 4.3
So CX=CS +SX = 15+4.3 = 19.3 or approx 20
Correct option is the first option .
