The objective of this excercise is to clear the variable t. We need to pass every term with a t to one side of the inequality and every term without it to the other side:
[tex]7t+15<3t-8[/tex][tex]7t-3t<-8-15[/tex][tex]4t<-23[/tex]then we have:
[tex]t<\frac{-23}{4}[/tex]And finally we have that:
[tex]t<-5.75[/tex]