Final answer:
To isolate the variable in the inequality m < -21, Tyson needs to divide both sides of the inequality by -1.
Step-by-step explanation:
To isolate the variable in the inequality m < -21, Tyson needs to perform the same operation on both sides of the inequality.
Since the inequality sign is less than (<), Tyson needs to divide both sides by a positive number. In this case, he can divide both sides by -1 to maintain the inequality sign.
Dividing both sides by -1 gives us m > 21.
Therefore, to isolate the variable, Tyson should divide both sides of the inequality by -1.