Question 119684
q = number of quarters
d = number of dimes
{{{25q + 10d = 570}}}
{{{q + d = 30}}}
{{{d = 30 - q}}}
{{{25q + 10(30 - q) = 570}}}
{{{25q + 300 - 10q = 570}}}
{{{15q = 270}}}
{{{q = 18}}}
{{{d = 30 - q}}}
{{{d = 30 - 18}}}
{{{d = 12}}}
She has 18 quarters and 12 dimes
check:
{{{25q + 10d = 570}}}
{{{25*18 + 10*12 = 570}}}
{{{450 + 120 = 570}}}
{{{570 = 570}}}
OK