Probability none of the screw is defective= $\frac{7}{10}*\frac{6}{9}$=$\frac{7}{15}$
Probability first one defective and second one is not defective=$\frac{3}{10}*\frac{7}{9}$=$\frac{7}{30}$
Probability first one is not defective and second one is defective=$\frac{7}{10}*\frac{3}{9}$=$\frac{7}{30}$
Probability both are defective =$\frac{3}{10}*\frac{2}{9}$=$\frac{1}{15}$