Answer:
a = -36/7
Step-by-step explanation:
55 + 7a = 19
(55 - 55) + 7a = (19 - 55)
7a = -36
7a/7 = -36/7
a = -36/7 the fraction can't be simplified any further
Finding the slope using two points:
The formula for slope is
In this case...
(1, 9) and (-3, 16)
^^^Plug these numbers into the formula for slope...

C. 
^^^This is your slope
Hope this helped!
~Just a girl in love with Shawn Mendes
23,009,040 = 2.300904 x 107
3x - 7 + 7 = 12 + 7
3x = 19
3x/3 = 19/3
X = 19/3 = 6 1/3