Take the like terms of the equation.
[tex]3 \sqrt{10} - 6 \sqrt{10}[/tex]
[tex]7 \sqrt{15} - 4 \sqrt{15} [/tex]
Subtract those like terms together.
[tex]3 \sqrt{10} - 6 \sqrt{10} = -3 \sqrt{10}[/tex]
[tex]7 \sqrt{15} - 4 \sqrt{15} = 3 \sqrt{15}[/tex]
The simplified form of this equation is [tex]-3 \sqrt{10} + 3 \sqrt{15} [/tex].