Question

Been struggling with these problems can anyone help me
19,21,23,25,27,28,30

Answer 1

21 = 4.8
8 x 2.1 = 16.8 - 12 = 4.8

Answer 2

19- would be -6+8 which equals 2

21- 8(2.1)-12 which equals 16.8-12 which is 4.8
23- 17 divided by 10 equals 1.7