Answer:
[tex]\boxed{r=-6}[/tex]
Step-by-step explanation:
[tex]All~you~have~to~do~is~collect ~the ~constants~ on ~one ~side ~of ~the~ =~ and[/tex] [tex]the~variables~(including~terms~with~r)~ on ~the~ other~ side.~ Then,[/tex] [tex]manipulate~it,~ so~ that~ you~ only~ have~ a ~single ~r~on~ its~ own~ on~ one~ side[/tex] [tex]and ~everything~ else~ on~ the ~other.[/tex]
Applying the method :
→ [tex]Subtract ~6r~from~ both ~sides:[/tex]
[tex]6r-6r+7~~=~~13+7r-6r[/tex]
[tex]0+7~~=~~13+r[/tex]
→ [tex]Subtract~13~from~both~sides:[/tex]
[tex]7-13~~=~~13-13+r[/tex]
[tex]-6~~=~~0+r[/tex]
[tex]r=-6[/tex]
The short cut approach for add or subtract is:
[tex]Move~ something~ to~ the~ other ~side ~of~ the~ ``=" ~and ~change~its~ sign.[/tex]
