8) a. 3 x 2 = 6 x 10 = 60
1 x 7 = 7 x 10 = 70
2 x 4 = 8 x 10 = 80
3 x 3 = 9 x 10 = 90
5 x 2 = 10 x 10 = 100
b. 7 + 2 = 9 + 10 = 19
4 + 6 = 10 + 10 = 20
3 + 5 = 8 + 10 = 18
1 + 8 = 9 + 10 = 19
9 + 6 = 15 + 10 = 25
11) 80 - a = 63 80 - 63 = 17 ( a )
20 + b = 60 20 + 60 = 80 ( b )
c - 70 = 30 70 + 30 = 100 ( c )
d + 30 = 49 49 + 30 = 79 ( d )