So to set up the equation we have:
<span><span><span>4M</span><span>4+M</span></span>=<span>127</span></span>
<span>28M=12(4+M)</span>
<span>28M=48+12M</span>
<span>28K−12M=48</span>
<span>(28−12)M=48</span>
<span>16K=48</span>
<span>M=<span>4816</span></span>
<span>M=3</span>
So Marna can clean the chimney alone in 3 hours
0, the slope and y-intercept is 0
the only like-terms are on the right-hand-side, since the left-hand-side has only 1 term anyway.

Answer:
3r − 9 = –6r
-9 = -6r-3r (you change the signs when bringing +3r to the other side)
-9 = -9r
r = -9/-9
r = 1