Chapter 7 Exponential and Logarithmic Functions - 7.7 Write and Apply Exponential and Power Functions - 7.7 Exercises - Skill Practice - Page 534: 17

$y=1.251\cdot x^{1.262}$

Let $y=ax^b$. Then our equations are: $3=a2^b$ and $12=a6^b$. If we divide the second equation by the first one we get: $4=3^b\\b=\ln_{3}{4}\approx1.262$. Then $3=a2^{1.262}\\a=\frac{3}{2^{1.262}}\approx1.251$. Thus $y=1.251\cdot x^{1.262}$