Agas is contained in a thick walled balloon. when the pressure changes from 417 mm hg to 576 mm hg, the volume changes from l to 4.78 l and the temperature changes from 497 k to 386k

We can use the combined gas law equation to solve for the initial volume

parameters for the first instance are on the left side and parameters for the second instance are on the right side of the equation 
substituting the values in the equation 

V = 8.50 L
the initial volume is 8.50 L

Idid the calculation and i get 875,000,000 which can be written as 8.75 x 10^6?

☆ionisation energy increases across a period from na -> ar☆ionisation energy decreases down a group from li -> fr☆ionic radius decreases across a period from na -> cl☆ionic radius increases down a groupfrom f -> ii hope it clarifies your doubts