Answer
a) $T(x)=M(x)+F(x)=2.99x+235.5$
b) $T(20)=295.3$.
c) Underestimate by $2.7$
Work Step by Step
$M(x)=1.53x+114.8$
$F(x)=1.46x+120.7$
a) The total function will be: $$T(x)=M(x)+F(x)=2.99x+235.5$$
b) The year $2005$ will be $2005-1985=20$th year after $1985$ so $x=20$. Inserting this into the function $T$ we get: $$T(20)=2.99(20)+235.5=295.3$$
c) From the bar graph the total population in $2005$ is $$147+151=298.$$ Because $295.3<298$, it means that the result in part $(b)$ underestimates the total population shown in the bar of $298-295.3=2.7$.
