why this proportion that until two days ago gave me a correct value of 1800 Billion now gives me error?

36E9 / 2 = x / 100, solve for x
cross multiply

36E11 = 2x
divide both sides by 2
x =36E11 / 2 =1,800,000,000,000

thanks for your kind reply; but I wanted to know why the scientific calculator gives me error?

36E9:2=x:100