13+7= 16-9= 49-5= 48+9= 40+(15-8)=
77-7= 20+67= 18-8= 74-60= 93-(68-60)=
35+5= 60-40= 20+70= 17-8= 73-(13+7)=
48-30= 14-5= 64+30= 50-6= 56+5-20=