Let x be number of 10 dollar bills

And y be number of 20 dollar bills

x + y = 11

10x + 10y = 110

10x + 20y = 170

10 y = 60

y = 6

x = 5

5 , ten dollar bills

6 , 20 dollar bills

If you are supposed to use algebra:

Let x = number of tens,

Let y = number of twenties

x + y = 11 (there are 11 total pieces of paper)

10x + 20y = 170 (10 times the number of tens plus 20 times the number of twenties = the amount of money)

Simplify that by dividing by ten.in

x + 2y = 17

Subtract x + y = 11 from.that

y = 6

So x = 11 -6 = 5

Check 5(10) +6(20) = 50+120 = 170 checks

If he uses 'x' ten dollar bills and 'y' twenty dollar bills:

x + y = 11 (total of eleven bills)

10x + 20y = 170 (total cost is $170)

Then solve the simultaneous equations:

x = 11 - y

10(11 - y) + 20y = 170

110 - 10y + 20y = 170

10y = 60

y = 6 (six twenty dollar bills)

x = 11 - 6 = 5 (five ten dollar bills)

If they were all 10s, that would take 17

3 20s, that is 3+11

4 20s, that is 4+9

5 20s, that is 5+7

6 20s, that is 6+5 = 11 ⬅