we have twice as many dimes as nickels, so we could have something like 18 dimes and 9 nickels. Algebraically we would write d = 18 and n = 9. The equation that fits this is d = 2n. The answer is between A and B at this point.
We rule out choice B since the 0.05d is incorrect. It should be 0.10d to represent the total value of all the dimes.
Choice A is correct
d = number of dimes
0.10d = value of all the dimes in dollars
n = number of nickels
0.05n = value of all the nickels in dollars
0.10d + 0.05n = total value from both coins combined
