So for this we will place 90 in place of x to solve our problem. So lets do it
x=90(x/100 + 1/3)
=90/100 + 1/3 ( and now out here we will first cut the zeroes of 90 and 100 which makes it easier for us to solve )
= 9/10 + 1/3 ( okay so now we will get the same denominators by taking the LCM of 3 and 10 which is 30 and then as 10 times 3 is 30 so we shall multiply 9 as well by 3 and as 3 is ten times 30 so we shall multiply 1 as well by 10 )
= 27/30 + 10/30
And now I hope u can do th rest yourself ! And still if u don't understand then pls be free to ask!