Question 122512
Put the amount in the phone in terms of pennies
{{{d}}} = number of dimes
{{{n}}} = number of nickels
{{{n + d = 80}}}
{{{5n + 10d = 665}}}
{{{d = 80 - n}}}
{{{5n + 10(80 - n) = 665}}}
{{{5n + 800 - 10n = 665}}}
{{{-5n = -135}}}
{{{n = 27}}}
{{{n + d = 80}}}
{{{d = 80 - 27}}}
{{{d = 53}}}
There are 53 dimes and 27 nickels in the phone
check
{{{5n + 10d = 665}}}
{{{5*27 + 10*53 = 665}}}
{{{135 + 530 = 665}}}
{{{665 = 665}}}
OK