## Introductory Algebra for College Students (7th Edition)

$a.\quad W=173n+293$ $b.\quad 1850$ million, which overstimates the actual value by 98 million.
a. $W=3(50n+95)+2(\displaystyle \frac{23}{2}n+4)\qquad$... distribute $W=(150n+285)+(23n+8)\qquad$... get rid of parentheses $W=150n+285 + 23n+8 \qquad$...rearrange and group like terms $W=(150n+23n)+(285+8)$ $W=173n+293$ b. In $2009$ (9 years after 2000), $n=9$. Substituting, $W=173(9)+293$ $=1557+293$ $=1850$ (million) The graph shows 1752 million for 2009, so our model overestimates the actual number by $1850-1752=98$ (million)