60+30:3=...,70-80:40,(17+9)*3+8=...,18+(12+5)*4=...
1)60+30:3=60+10=70 2) 70-80:40=70-2=68 3)(17+9)*3+8=26*3+8=78+8=86 4)18+(12+5)*4=18+17*4=18+68=86