The Sum of an Arithmetic Series

An Arithmetic Progression has 3 as its first term. Also, the sum of the first 8 terms in twice the sum of the first 5 terms. Find the common difference!

Find the sum of the Arithmetic Series with first term 1, common difference 3 and last term 100!

The sum of the first 20 terms of an Arithmetic Series is identical to the sum of the first 22 terms. If the common difference is -2, find the first term!