In order to solve this, you need a diagram.
From this diagram, you can set up an expression.
Let's say the total distance is represented by the variable T.
[tex]T=x+y[/tex]
To solve for x and y, you need to do the Pythagorean Theorem.
[tex]x^2=3^2+4^2 \\ x^2=9+16 \\ x^2=25 \\ \sqrt{ x^2} = \sqrt{25} \\ x=5 \\ \\ y^2=6^2+8^2 \\ y^2=36+64 \\ y^2=100 \\ \sqrt{ y^2} = \sqrt{100} \\ y=10[/tex]
Now plug these values back into the expression and you will have your final answer.
[tex]T=(5)+(10) \\ T=15 \\ \\ 15_{miles}[/tex]