Aplane flies over city a and reaches city b, 115 miles away, in 15 minutes. find the speed of the plane in miles per hour assuming the plane flew at a constant speed.

Just divide the miles travelled by the time:
115/15= 7.67 miles per minute
Then convert the minutes to hours by multiplying the 7.67 and the 1 by 60 (remember that "per" indicates "over one", so 7.67 miles/1 minute):
7.67*60/1*60= 460.2 miles per hour. 

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