98+97-96-95+94+93-92-91+90+89…-4-3+2+1
=98+(97-96)-(95-94)+(93-92)-(91-90)+(89-88)…+(5-4)-(3-2)+1
=98+1-1+1-1+1-1…+1-1+1
=98+1
=99
98+97-96-95+94+93-92-91+90+89…-4-3+2+1
=98+(97-96)-(95-94)+(93-92)-(91-90)+(89-88)…+(5-4)-(3-2)+1
=98+1-1+1-1+1-1…+1-1+1
=98+1
=99