Do 18 ppl i need to get a good grade

I believe the answer is 52.80 

Also 15 is, 7a + 18. Hope this helps :D

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