3 girls A, B & C had the same number of coins. A & B each had a mix of fifty cents coins and 10 cents coins. A had 9 ten cents coins while B had 15 ten cents coins. C had only fifty cents coins.
B used all her fifty cent coins to buy some food. she then had $10 less in coins than C. How many fifty-cent coins did C have?
pls kindly explain. thank u.