Martin has 18 coins, all dimes and quarters, worth $2.85. how many dimes does he have

Since 1 quarter equals 25 cents, 3 will equal 75.

Then how do you get 85?

Well 75 + what (x) is 85?

Or 85 - 75 is what?

85 - 75 is 10.

10 cents is a dime. So add a dime to it. So now you have a total of 4 coins. You need to find the leftover 14 coin values.

So, 10 dimes is a dollar and 4 quarters is a also dollar.

10 + 4 is 14 and a dollar + a dollar is 2 dollars.

2 dollars + those 4 coins, 85 cents is $2.85.

You're final answer is : Martian has 11 dimes and 7 quarters.