The first step to solve this problem is to realize that this information can be "translate" into a linear system of two equations. Let's denote by F the number of lawns he cuts on Fridays and let's denote by S the corresponding on Saturdays. So we have
[tex]22.50\cdot F+22.50\cdot S=135[/tex][tex]F=3[/tex]Replacing the value of F into the first equation we get
[tex]22.50\cdot3+22.50\cdot S=135[/tex][tex]67.5+22.5\cdot S=135[/tex][tex]22.5\cdot S=67.5[/tex][tex]S=\frac{67.5}{22.5}=3[/tex]
