Astore experienced a 14.2% fall in takings in february, compared to the previous month.
their takings in february were £742,513.20
how much did they take in january?

say the amount in jan is x we know if we subtract off 14.2% of x (from x) we get Feb's amount

so x - 0.142x = 742,513.20 (notice we change 14.2% to 14.2/100 -- that is what % is short for -- or ,as a decimal 0.142)

we have 1x - 0.142x or (1-0.142)x on the left side
0.858 x = 742513.20

divide both sides by 0.858 to "solve for x"

x= 865,400