Exercise 60 Page 206

Inequalities can be solved in the same way as equations, by performing inverse operations on both sides until the variable is isolated. The only difference is that when we divide or multiply by a negative number, we must reverse the inequality sign.

t-21<-12

AddIneq

LHS+21

t<9

The above tells us that all values less than 9 satisfy the inequality. Let's graph the solution set on a number line. Notice that t cannot be 9, which we show with an open circle on the number line.