Question 20511
Let x = the number of quarters ($0.25) and (144-x) = the number of nickels ($0.05) and they all add up to $28.40. So now you can write the necessary equation:
{{{x(0.25) + (144-x)(0.05) = 28.40}}} Simplify and solve for x.
{{{0.25x + 7.2 - 0.05x = 28.40}}}
{{{0.2x + 7.2 = 28.4}}} Subtract 7.2 from both sides.
{{{0.2x = 21.2}}} Divide both sides by 0.2
{{{x = 106}}}

There are 106 quarters and (144-106 = 38) 38 nickels.