Answer:
Let Marshall's salary be Â
S
m
Let Jim's salary be
  Â
S
j
Let the count in years be Â
n
S
m
=
$
36000
+
4000
n
S
j
=
$
51000
+
1500
n
Set Â
S
m
=
S
j
For convenience lets drop the $ symbol
⇒
36000
+
4000
n
Â
=
Â
51000
+
1500
n
Subtract Â
1500
n
and
36000
from both sides
4000
n
−
1500
n
=
51000
−
36000
2500
n
=
15000
Divide both sides by 2500
n
=
15000
2500
=
150
25
=
6
Step-by-step explanation: