can you guys please help me with number 13 and with shown work

Answer:
Step-by-step explanation:
Let's solve for c.
6c−9d=111
Step 1: Add 9d to both sides.
6c−9d+9d=111+9d
6c=9d+111
Step 2: Divide both sides by 6.
6c
6
=
9d+111
6c=3/2 d+37/2
Answer:
c= 3/2 d+37/2
Second one
Let's solve for c.
5c−9d=103
Step 1: Add 9d to both sides.
5c−9d+9d=103+9d
5c=9d+103
Step 2: Divide both sides by 5.
5c
5
=
9d+103
5c =9/5 d+103/5
Answer:
c=8, d = -7
Step-by-step explanation:
6c - 9d = 111
5c - 9d = 103
Multiply the second equation by -1
-5c + 9d = -103
Add this to the first equation to eliminate d
6c - 9d = 111
-5c + 9d = -103
------------------------
c = 8
Now we need to find 9
6c - 9d = 111
Substitute in c=8
6(8) -9d = 111
48 - 9d = 111
Subtract 48 from each side
49-48 -9d = 111-48
-9d =63
Divide each side by -9
-9d/-9 = 63/-9
d = -7