maths
posted by ssssss .
Xuan Yun has a total of 24 coins in her piggy bank. Some of them are twentycent coins and the others are fiftycent coins. Thetotal savings is $6.90. How many twentycent and fiftycent coins does she have?

number of 25 cent coins  x
number of 50 cent coins  24x
25x + 50(24x) = 690
solve for x and backsubstitute