Question 1153416
{{{system(8a+4c=38,a+2c=8.5)}}}


{{{system(4a+2c=19,a+2c=8.5)}}}


Since the question asks for c, best to try to eliminate a.
{{{system(4a+2c=19,4a+8c=34)}}}
{{{E2-E1}}}
{{{6c=15}}}
{{{2c=5}}}
{{{highlight(c=2.50)}}}