Question

90:30 100:20 7.8-42:7 9.9-9.3

Answer 1

90:30=3
100:20=5
7*8=56  42:7=6    56-6=50
9*9=81   9*3=27   81-27=54

Answer 2

90:30=3
100:20=5
7·8-42:7=50
9·9-9·3=54