Chapter 5 - Exponential and Logarithmic Functions - 5.3 Exponential Functions - 5.3 Assess Your Understanding - Page 284: 121

$36$

Recall that in the exponential function $f(x)=Ca^x$,$a$ is a growth factor if $a>1$. The growth factor is $3$, so $a=3$. Thus $f(x)=C3^x$. Since $f(6)==12$, then $f(6)=C\cdot3^6\\ \frac{12}{3^6}=C$ Thus $f(7)=C\cdot a^7 \\f(7)=\frac{12}{3^6} \cdot 3^7\\ f(7)=12 \cdot 3^{7-6}\\ f(7)=12 \cdot 3\\ f(7) = 36$