45+345+30 58-358-30 50+1717+50
69-2187-20 3+5555-3 30个一3个十
28+8= 60+24= 6+24= 45-6+30=
15-7= 19-9= 9+79= 40+22-9=
75-6= 86-60= 35+30= 53+(25+5)=
57-6= 58-50= 40+50= 86-(20+10)=
20+11 75-30 55-10 30+30
31 45 60
25+20 80-20 38-7 15+30