Good night :). Sleep tight!
round to the nearest
hundredth of milligram : 4.27
tenth of milligram: 4.3
milligram : 4
I hope you understood!! :)
Vinegar is the x or horizontal oil is the y or vertical

the point represent the amount of vinegar and oil so for 1 tbsp vinegar you need 1.5tbsp oil
20% off means you pay 80% of the price so you multiply by 0.8, and 7% tax means you multiply by 1.07
Resulting cost = 18.99*0.8*1.07 = 16.26
Hope this helps let me know if im wrong!