Which equation can be used to find the answer?

After two months, Rachel has saved enough money to buy an MP3 player. During the second month, she saved $87 and she pays $199 for the MP3 player.

How much did Rachel save during the first month?

A.
m = 87 • 2
m = 174
$174

B.
199 + 87 = m
m = 286
$286

C.
m + 87 = 199
m = 112
$112

D.
m – 87 = 199
m = 287
$287

Question

Which equation can be used to find the answer? 
 
After two months, Rachel has saved enough money to buy an MP3 player. During the second month, she saved $87 and she pays $199 for the MP3 player. 
 
How much did Rachel save during the first month?
 
 A.
m = 87 • 2
m = 174
$174
 
 B.
199 + 87 = m
m = 286
$286
 
 C.
m + 87 = 199
m = 112
$112
 
 D.
m – 87 = 199
m = 287
$287