The local car dealership sells both foreign and domestic cars. last month the dealer sold 5 domestic cars for every 2 foreign cars that were sold. if 21 cars were sold, how many were domestic?

15 cars were domestic 

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