Answer:
T1=12 a=12 a=T1
d=9
your Arithmetic equation is Tn=a+(n-1)d
Tn=a+(n-1)d
SUBSTITUTE a and d in your equation
Tn=12+(n-1)(9)
Tn=12+9n-9
Tn=3+9n or Tn=9n+3
You square the new total area which you are given for the garden and then you subtract by 9 meters and then you get 4 m.
The slope is 3 because you need to use the slope-intercept form y=mx+b to find the slope of m