Let [tex]M[/tex] denote the event that UTC beats Marshall, so that [tex]\mathbb P(M)=0.63[/tex], and let [tex]F[/tex] denote the event that UTC beats Furman, so that [tex]\mathbb P(F)=0.55[/tex]. We're told that the UTC has a [tex]\mathbb P(M\cap F)=0.3465[/tex] probability of beating both Marshall and Furman.
So, by the definition of conditional probability, the probability of UTC beating Furman after having beaten Marshall is
[tex]\mathbb P(F\mid M)=\dfrac{\mathbb P(F\cap M)}{\mathbb P(M)}=\dfrac{0.3465}{0.63}=0.55[/tex]