Steve had 38 coins.They were twenty-cent and ten-cent coins.Their total value was $5.30.How many twenty-cent coins were there?

Call the number of 20 cent coins "x"

Let the number of 10 cent coins be 38 - x

So, the number of coins times their value each gives us the total value....so we have

20x + 10(38 - x)  = 530   simplify

20x + 380 - 10x = 530

10x + 380 = 530    subtract 380 from each side

10x = 150    divide both sides by 10

x = 15   ....and that's the number of 20 cent coins