There are 5 red pens, 3 blue pens and 2 green pens in a box. Ziyad takes at random a pen from the box and gives the pen to his friend, Tamer. Ziyad then randomly takes another pen from the box. Work out the probability that both pens are the same color.

An energy drink company claims that its product increases students' memory levels. to support its claims, the company issues advertisements claiming that 8 out of 10 people (chosen randomly from across the country) who tried their product reported improved memory. the missing component in this study is a .

Could somebody me with this radical simplification?

Select the two pairs of figures that are similar.