Recall that the probability must add 1, therefore:
[tex]0.6+x=1[/tex]Solving for x, we get:
[tex]\begin{gathered} x=1-0.6 \\ x=0.4 \end{gathered}[/tex]Therefore, the probability of Thomas inviting Madeline to the party over the phone is:
[tex]0.2\cdot0.4=0.08[/tex]or 8%.