Question 56273
The problem is:
Suppose that a lot costs $60,000 and a builder charges $84 per square foot of living area in a house. How big, to the nearest square foot, is a house that can be purchased for $180,000?  
Your model should be:
{{{180000=84x+60000}}}
{{{180000-60000=84x}}}
{{{120000=84x}}}
{{{120000/84=84x/84}}}
{{{1428.57=x}}}  That was one of your choices if you round off to the nearest whole number: x=1429 sq ft.

Happy Calculating!!!