A=5+6+7+8+9+10+11+12+13+14+15
A=(5+15)+(6+14)+(7+13)+(8+12)+(9+11)+10
A=20+20+20+20+20+10
A=20x5+10
A=100+10
A=110
A = 5 + 6 + 7 + 8 + 9 + 10 + 11 + 12 + 13 + 14 + 15
A = ( 5 + 15 ) + ( 6 + 14 ) + ( 7 + 13 ) + ( 8 + 12 ) + ( 9 + 11 ) + 10
A = 20 + 20 + 20 + 20 + 20 + 10
A = 110