The sum of the first 5 terms of an arithmetic series is $70$.  The sum of the first 10 terms of this  arithmetic series is $210$.  What is the first term of the series?
Question:
The sum of the first 5 terms of an arithmetic series is $70$.  The sum of the first 10 terms of this  arithmetic series is $210$.  What is the first term of the series?
Answer:
Let's think step by step.

user
\frac{42}{5}
The sum of the first 5 terms of an arithmetic series is $70$.  The sum of the first 10 terms of this  arithmetic series is $210$.  What is the first term of the series?
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