Answer:
In 1.8 are 9 fifth, since 1 is 5 fifth and 0.8 is 4 fifth.
In - 3 2/3 are 11 thirds, since 3 is 9 thirds and 2/3 obviously is 2 thirds.
2 7/100 as a decimal is 2.07, since 2.7 would be 2 7/10 and 2.007 would be 2 7/1000.
7/8 as a decimal is 0.875, just type 7÷8 into a calculator and you got it.
21/30 as a decimal is 0.7, you can also just type 21÷30 into a calculator here.