Answer:
First two boxes are 6
Third box is -18
the last row is 3/1 (-18/1) = (1/3a) 3/1
Step-by-step explanation:
Ima try my best to explain:
-6 = 12 + 1/3a
+6 +6
0 = 18 + 1/3 a subtract 18 on both in order to get 1/3a by itself
-18 -18
-18 = 1/3a
-18/ 1/3 = 1/3a / 1/3 to make it easier multiply by the reciprocal on both sides
3/1 x -18/1 = 1/3 x 3/1
multiply across will get you -54/1 which is just -54
