Final answer:
Mr. Tieu purchased 15 apples, 5 oranges, and 9 bananas.
Step-by-step explanation:
Let's denote the number of oranges as O, the number of apples as A, and the number of bananas as B.
From the given information, we know that A = O + 10 (10 more apples than oranges) and B = A - 6 (6 fewer bananas than apples).
We can now form an equation based on the total cost and quantities of each type of fruit: 0.7A + 0.8O + 0.5B = 23 (0.7 being the cost of an apple in dollars, 0.8 being the cost of an orange, and 0.5 being the cost of a banana).
Substituting the values for A and B in terms of O, we get 0.7(O + 10) + 0.8O + 0.5(O + 10 - 6) = 23. Solving this equation, we find that O = 5, A = 15, and B = 9.