Question 912677
Let the value of the houses she sells in a year be x

100 per week
50 weeks in a year

I = 5000+3.5% *x

I> 20,000

5000+3.5%x>20,000

multiply by 100

500000+3.5x > 2000000

3.5x >2000000-500000

3.5x >1500000

x>1500000/3.5

x>428,752