Question 1044426
Of the 3,200 houses, {{{(3/4)*3200 = 2400}}} are older than 100 years.

{{{(1/3)*2400 = 800}}} were renovated, and so 2,400 - 800 = 1,600 stayed unrenovated.  

800 new houses built means that there are now 4,000 houses in total.

===> {{{1600/4000 = 2/5}}}, or 40% of the houses are not renovated.