Chapter 8 - Section 8.1 - Review of Equations of Lines and Writing Parallel and Perpendicular Lines - Exercise Set - Page 574: 60

a) $y=12000x+18000$ b) $102,000 c) After 9 years

a) $(1,30000)$ and $(4,66000)$ $m=(66000-30000)/(4-1)$ $m=36000/3$ $m=12000$ $y=mx+b$ $30000=12000*1+b$ $30000=12000+b$ $18000=b$ $y=12000x+18000$ b) $y=12000x+18000$ $y=12000*7+18000$ $y=84000+18000$ $y=102000$ c) $126000=12000x+18000$ $108000=12000x$ $108000/12000=12000x/12000$ $9=x$