Answer :
(-1,13)
1) Let's find the Coordinates of B, using the Midpoint Formula for that:
[tex]M=(\frac{x_A+x_B}{2},\frac{y_A+y_B}{2})[/tex]2) Plugging into that the given information:
[tex]\begin{gathered} M=(\frac{x_A+x_B}{2},\frac{y_A+y_B}{2}) \\ (3,10)=(\frac{-5_{}+x_B}{2},\frac{7_{}+y_B}{2}) \\ \\ \frac{-5+x_B_{}}{2}=-3 \\ -5+x_B=-6 \\ x_B=-6+5 \\ x_B=-1 \\ \frac{7_{}+y_B}{2}=10 \\ 7+y_B=20 \\ y_B=20-7 \\ y_B=13 \end{gathered}[/tex]3) Hence, the coordinates of point B are (-1,13)