15-6= 13-5= 54-4= 11-7+6=
17-8= 11-6= 70-10= 14-9-2=
14-6= 75+4= 30+24= 20+30+40=
12-5= 18-9= 37+2= 40+60-70=
9×9+19
=9×9+9+10
=9×(9+1)+10
=9×10+10
=(9+1)×10
=10×10
99×99+199