Question

Getting a defective item when two items are randomly selected from a box of two defective and three non-defective items       

Answer 1

Let A - ''getting a defective item'', then $P(A)=1-P(\neg A)$

$P(\neg A)={\frac m n}$ , where n - number of options of taking two items out of five, m - number of options of taking none defective item

$P(A)=1-{\frac {{ 3\choose 2}} {{5 \choose 2}}}=1-{\frac 3 {10}}={\frac 7 {10}}$