Answer:
[tex]{ \tt{9 \div 3 \{(20 - 7) - 2 {}^{2} \} }} \\ \\ { \tt{ = 9 \div 3(13 - 4)}} \\ \\ { \tt{ = 9 \div 3(9)}} \\ \\ = { \tt{(9 \div 9)(1 \div 3)}} \\ \\ \dashrightarrow \: { \boxed{ \tt{ \: \: = \frac{1}{3} \: \: }}}[/tex]
