Roe had 4 more 20-cent coins than 50-cent coins in his piggy bank. Given that he had $17.60 in total, how many 20-cent coins did Roe have?
number of 50 cent coins --- x
number of 20 cent coins ---- x+4
Now switch your thinking to "value of those coins"
50x + 20(x+4) = 1760
50x + 20x + 80 = 1760
70x = 1680
x = 24
state your conclusion.