Question
Eric folded 20 paper swans on the first day. Each day he did 7 more paper swans than the previous day. On the last day, he made 90 swans. How many days did he fold paper swans?
2 m

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Eric folded 20 paper swans on the first day. Each day he did 7 more paper swans than the previous day. On the last day, he made 90 swans. How many days did he fold paper swans?