we know that In similar triangles. The ratio of the lengths of the sides CS and CB must be equal to the ratio of the lengths of sides CR and CA. CS / CB = CR / CA which can also be written as, CS / (CS + SB) = CR / (CR + RA) CS*(CR+RA)=CR*(CS+RA) CS=2x+1 SB=6x CR=7.5 RA=18 (2x+1)*[7.5+18]=7.5*[2x+1+18] (2x+1)*[25.5]=7.5*[2x+19] (51x+25.5)=15x+142.5 51x-15x=142.5-25.5 36x=117 x=117/36 x=3.25