If some percentage is greater then its original price (i.e. 100%) we have to add it and vice versa.

For example : in the above for the stock market, the price decreases 10% so we substrate it from 100%

90% and 0.9 is also equal to 90%, u just have to divide it by 100.

For next statement 4% increase so 104% i.e. 1.04.

consider opening price of stock on Monday = x (I know its 100)

closing price on Monday = 1.1x (since its 110)

closing price on tuesday = 10% less than closing price on monday = (1-0.1)*1.1x = 0.9 * 1.1x

closing price on wednesday = 4% greater than that of tuesday = (1 + 0.04) \times (tuesday’s price) = 1.04 \times 0.9 \times 1.1x = 1.0296x ~ 1.03x = 3 percent more than x

On Tuesday, closing price of the stock was 10 percent lesser than the closing price on monday (which was $110).

This means the closing price on Tuesday will be 110 - 110*(10)/100 (since it is 10 percent lesser)

This equals 110*(90)/100 which is 110*0.9.
Similarly on Wednesday, the closing price of the stock was 4% greater than what it was on Tuesday (which was 110*0.9) giving us 110

*0.9 + 110*0.9*(4)/100 and simplifying this gives us 110

*0.9*1.04.

thanks i got it