Question 726766
Let x be the number of nickels.
Then (77-x) is the number of dimes.

{{{0.05x + (0.1)(77-x) = 6.1}}}
{{{0.05x + 7.7 - 0.1x = 6.1}}}
{{{0.05x + 7.7 - 0.1x = 6.1}}}
{{{-0.05x = -1.6}}}
{{{x = 32}}}

∴ Marcus has 32 nickels and (77-32=45) dimes.