Question

what do I multiply 3P + 2D = 16.50 with??

Answer 1

we need to solve the system of equations, there are different methods, I think here the simplest one is multiplying the first equation by 2 and then substract the second equation

$\begin{gathered} 2(3P+2D=16.5) \\ 6P+4D=33 \end{gathered}$

Then, we have the equation

$\begin{gathered} 2P=7 \\ P=\frac{7}{2} \\ P=3.5 \end{gathered}$

So, replacing P in the first equation

$\begin{gathered} 3(3.5)+2D=16.5 \\ 10.5+2D=16.5 \\ 2D=16.5-10.5 \\ 2D=6 \\ D=\frac{6}{2} \\ D=3 \end{gathered}$

We can check our result replacing P=3.5 and D=3 in the second equation

$4(3.5)+4(3)=14+12=26$

Then, our answer is correct and P=3.5 and D=3