27.7-14=Cost above 500 msg
13.7=C
E=number of Extra messages sent
C=0.1E
13.7/0.1=E
137=E
Total messages=T
T=500+E
T=500+137
T=637
Danielle sent 637 messages in September
Final Answer: 
Steps/Reasons/Explanation:
Question: Which expression is equivalent to 
<u>Step 1</u>: Expand by distributing terms.
×
× 
<u>Step 2</u>: Simplify
×
to
.
× 
<u>Step 3</u>: Simplify
×
to
.

<u>Step 4</u>: Remove parentheses and add.

~I hope I helped you :)~
Answer:
125
Step-by-step explanation:
600=150+225+100+X=475+X
600-475=125=X
X=125