I would approach this from a Guess and Check Strategy. Take combinations of two numbers when added equal six: 0 + 6 1+ 5. 2+ 4, 3 + 3, 4 + 2, 5 + 1, 6 + 0. Take a combination like 3 + 3. If the student bought 3 notebooks at $8 each and 3 notebooks at $10 each it would be $24 + $30 = $54 which is just short of $56. You could use each of the combinations in the same way until you match $56. In the end the combination of 2 + 4 would solve the problem. Two notebooks at $8 each plus four notebooks at $10 each would be: $16 + $40 which does equal $56. So the student bought 2 notebooks at $8 each and 4 notebooks at $0 each.
The first thing you have to do is find a way to make the last digit 6 (since its $56). So that would be $8×2=16, so there are 2 small notebooks. Then, she needs another $40 to get $56, so 40÷10=4, so she bought 4 large notebooks.
