Question 219874
Let {{{n}}} = number of nickels
Let {{{q}}} = number of quarters
given:
(1) {{{n + q = 15}}}
(2) {{{5n + 25q = 155}}} (in cents)
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From (1)
{{{q = 15 - n}}}
Subsitute in (2)
(2) {{{5n + 25q = 155}}}
{{{5n + 25*(15 - n) = 155}}}
{{{5n + 375 - 25n = 155}}}
{{{-20n = -220}}}
{{{n = 11}}}
And 
{{{q = 15 - n}}}
{{{q = 15 - 11}}}
{{{q = 4}}}
You have 11 nickels and 4 quarters