so.. let's say iron (f) plus potassium(k) plus mulch(m) all those quantities added together, whatever they are, add up to 19lbs
thus
f + k + m = 19
there is 16 times more mulch than iron, thus m = 16f
and twice as much as potassium, thus m = 2k
so [tex]\bf f+k+m=19\qquad
\begin{cases}
f=iron\\
k=potassium\\
m=mulch\\
--------------\\
m=16f\to \frac{m}{16}=\boxed{f}
\\\\
m=2k\to \frac{m}{2}=\boxed{k}
\end{cases}
\\\\\\
\cfrac{m}{16}+\cfrac{m}{2}+m=19[/tex]
solve for "m", to see how much mulch there is
how much iron? well, m/16 = f
how much potassium? well, m/2 = k
