Answer:
3 nickels and 7 dimes.
Step-by-step explanation:
Let +n+ = number of nickels
Let +d+ = number of dimes
-----------------------------
(1) +5n+%2B+10d+=+85+
(2) +d+=+n+%2B+4+
----------------------------
Substitute (2) into (1)
(1) +5n+%2B+10%2A%28+n+%2B+4+%29+=+85+
(1) +5n+%2B+10n+%2B+40+=+85+
(1) +15n+=+45+
(1) +n+=+3+
and
(2) +d+=+n+%2B+4+
(2) +d+=+3+%2B+4+
(2) +d+=+7+
---------------------
There are 3 nickels and 7 dimes
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check:
(1) +5n+%2B+10d+=+85+
(1) +5%2A3+%2B+10%2A7+=+85+
(1) +15+%2B+70+=+85+
(1) +85+%2B+85+
OK
