Question 1010260
Let's call the number of $5 and $10 bills, x and y.
Thus we have
y = 3x - 10  and their value
5x + 10y = 600
Now substitute
5x + 10(3x - 10) = 600
5x + 30x - 100 = 600
35x = 700
x = 20 $5 bills
y = 3(20) - 10 = 50 $10 bills