Answer:
x=0.5y0.25x+0.05y=2.80
Substitute x into
\begin{gathered}0.25(0.5y) + 0.05y = 2.80 \\ 0.175y = 2.80 \\ y = 16\end{gathered}0.25(0.5y)+0.05y=2.800.175y=2.80y=16
\begin{gathered}x = 0.5(16) \\ x = 8\end{gathered}x=0.5(16)x=8
Total coins = 8 + 16 = 24
Hope this helps. - M