To solve the given inequality for x, the first step is to leave the x-term alone on one side of the expression. To pass -4 to the left side of the inequality you have to apply the opposite operation to both sides of it:
[tex]\begin{gathered} 21<-4+5x \\ 21+4<-4+4+5x \\ 25<5x \end{gathered}[/tex]Then you have to divide both sides of the expression by 5 to reach the possible value of x:
[tex]\begin{gathered} \frac{25}{5}<\frac{5x}{5} \\ 5The possible values of x are those less than 5.