Question 152624
Which is x and which is y?
If x is the number of homes with first floor plan and y is the number of homes with second floor plan, then
"3 times as many homes available with second floor plan than the first" would be
1.{{{y=3x}}}
Then
2.{{{x+y=56}}}
would be the total number of homes with first and second floor plans is 56.
You would have two equations with two unknowns, x and y.
You could then solve for x and then y substituting eq. 1 into eq. 2. 
Please repost if you need more help.