66+4=70,
43+6=49, 7-5=2, 21-7=14, 28+28=56, 33+33=66, 60-40=20, 100-90=10, 47+3=50, 62+8=70, 71-3=68,80-7=73,
27/9=3, 63/7=9, 63/9=7, 9/9=1.
1) 7-5=2, 21-7=14, 60-40=20, 100-90=10, 27/9=3, 63/7=9, 63/9=7, 9/9=1.
2) 43+6=49, 47+3=50.
3) 66+4=70, 28+28=56, 33+33=66, 62+8=70, 71-3=68,80-7=73.