1. 9(17-13)/6
=9(4)/6
=36
=6

2. 25+14/(5-3)
=25+14/2
=12.5+7
=19.5

3. 20-3-{7-[2+(4-3)]}
=20-3-{7-[2+1]}
=20-3-{7-3}
=20-3-4
=20-7
=13