the ratio of boys to the total number of students in a school play is 4: 7. there are 9 girls in the school play. how many students are in the school play?

4:7

4/7 = boys

3/7 = girls

3*3 = 9
7*3= 21

9 out of the 21 students are girls.

There are 21 students in the school play.

This is just a little extra for your understanding:

4/7
4*3 = 12
7*3 = 21

12 out of the 21 students are boys. 
 

1. 0.3 •4 is the same as 4 groups of 0.32. 7•0.8 is the same as 7 groups of 0.83. it increases by 0.5 every time, so 0.5x4 it increases by 0.9 every time, so 0.9x5. 0.9•12=10.86. 0.47•5=2.35i can finish the next ones in a separate post