Step 1 :Differentiate the given equation with respect to time $t$ to get an equation involving $\frac{dp}{dt}$, $\frac{dx}{dt}$, $p$, and $x$.
Step 2 :The differentiated equation is $4\frac{dp}{dt}+3\frac{dx}{dt}+3p\frac{dx}{dt}+3x\frac{dp}{dt}=0$.
Step 3 :Substitute the given values $x=2$, $p=4$, and $\frac{dp}{dt}=1.2$ into the differentiated equation.
Step 4 :This gives $4(1.2)+3\frac{dx}{dt}+3(4)(2)+3(2)(1.2)=0$.
Step 5 :Solve this equation for $\frac{dx}{dt}$ to get $\frac{dx}{dt}=-0.80$.
Step 6 :\(\boxed{-0.80}\) is the rate at which $x$ is changing when $x=2$, $p=4$, and $\frac{dp}{dt}=1.2$.