I$\mathrm{.}24$ Percents up and down.$$ Between October $14,2017,$ and October $14,2018,$ the average price of regular gasoline increased from $$2\mathrm{.}46$ per gallon to $$2\mathrm{.}90$ per gallon.

a$.$ Verify that this is almost an $18\%$ increase in price.

b$.$ If the price of gasoline decreases by $18\%$ from it October $14,2018,$ level of $$2\mathrm{.}90$ per gallon, what would be the new price? Notice that an $18\%$ increase followed by an $`8\%$ decrease does not take us back to the starting point.