Question 910029
a+c=415,
5*a+3*c=1615
a=415-c
5*(415-c)+3*c=1615
2075-5c+3*c=1615
-2*c=-460
c=230
a=415-c
a=185 at $5 and  c=230 at $3
check
185+230=415
5*a+3*c=1615
5*185+3*230=1615
925+690=1615
1615=1615
ok