There are only two ways to have 67 cents in 6 coins:
1.   1 half dollar, 3 nickels and 2 pennies
2.   2 quarters, 1 dime, 1 nickel and 2 pennies
However, since half dollars are not in circulation, there is
just one way:
2 quarters, 1 dime, 1 nickel and 2 pennies
We want 
P(nickel first AND quarter second) =
P( "1 way out of 6 or 
" AND "2 ways out of 5 or 
) =
          
×
 = 
 = 
Edwin