The diameter of a circle is 34 yards. What is the circle's circumference?

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Liz had 140 pens and inna had 100 pens. after inna gave liz some pens, liz had 3 times as many pens as inna. how many pens did inna give liz?

How do i simply this expression (quadratic formula basis) on a ti-84 or normal calculator?