Question 1025381
{{{50S+180D=320}}}
1.{{{5S+18D=32}}}
.
.
{{{75S+100D=225}}}
2.{{{15S+20D=45}}}
Multiply eq. 1 by 3 and subtract from eq. 2,
{{{15S+20D-15S-54S=45-96}}}
{{{-34D=-51}}}
{{{D=1.50}}}
Now use either equation to solve for {{{S}}}.