Step-by-step explanation:
✲ 
Remove the unnecessary brackets :
⇢ 
Combine like terms. Like terms are those which have the same base. Only coefficients of like terms can be added or subtracted.
⇢ 
⇢ 

Hope I helped ! ♡
Have a wonderful day / night ! ツ
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Answer:
yoo
Step-by-step explanation:
3c-d
3c-(-c+7)
3c+c-7
4c-7
Final answer: 4c-7
The approximate middle value
25=2,500, 278= 27800%, 2.9=290, 3.0=300, 0.67= 67