Answer:
In the first picture I uploaded, I show the housing market equilibrium without any effective legal ceilings on rent. In this equilibrium, the quantity demanded and the quantity supply reach an equilibrum of 70, at a price of $1,100 per rent.
In the second picture I uploaded, we can see the price ceiling in red. The price ceiling does not allow the rent to reach equilibrium, which causes a demand of eighty houses, but a supply of sixty houses, leading to a housing shortage of 20 houses.
