Simplify
2+(4+9)-2{18-3[7-(8-6) +1}
Just do it step by step:
2+(4+9)-2{18-3[7-(8-6)+1}
2+(13)-2{18-3[7-(2)+1}
15-2{18-3[6]}
15-2{18-18}
15-2{0}
15-0
15
2+(4+9)-2{18-3[7-(8-6) +1}
2+(4+9)-2{18-3[7-(8-6)+1}
2+(13)-2{18-3[7-(2)+1}
15-2{18-3[6]}
15-2{18-18}
15-2{0}
15-0
15