I do not understand the question below

Question

Jim had some dimes, quarters, and nickels. First, he counted only the dimes and quarters and found that he had 9 coins. Then, he counted only the nickels and dimes and found there were 10 coins. He saw that he had 15 coins altogether. How much money does Jim have?

Answer 1

The question is asking you to figure out how many of each type of coin Jim has.

Each sentence is an equation:

d = dimes

q = quarters

n = nickles

d + q = 9

n + d = 10

d + q + n = 15

The last equation is your friend only if you have one variable. Use the first two equation to get rid of some variables from the last equation. I like:

q = 9 - d

n = 10 - d

Now plug in to the last equation:

d + (9 - d) + ( 10 - d) = 15

Solve for "d"

19 - d = 15

d = 4

You can use "d" and plug in the initial two equations:

d + q = 9

n + d = 10

This will allow you to solve for "q" and "n"