Forgot this topic but the br/ shit is ther because you pressed enter after using \\ to go to a new line, keep it on the same line so its contiuous writing -
\text{Let b}=\left ( v_{1},v_{2},v_{3} \right )\text{be a basis of }\mathbb{R}^{3}\text{and define c}=(v_{2},v_{3},v_{1}).\\ \text{Suppose...