Adding the radical terms like the variables
To add them they must have the same roots
[tex]\because-10\sqrt[]{7}+12\sqrt[]{7}[/tex]Since both terms have the same root (root 7), then we will add their out numbers
[tex]\therefore\sqrt[]{7}(-10+12)[/tex]We will add -10 and 7, then write the answer with root 7
[tex]\therefore-10\sqrt[]{7}+12\sqrt[]{7}=\sqrt[]{7}(-10+12)=2\sqrt[]{7}[/tex]