Apple Orange Price
1. **State the problem:** A man buys some apples and oranges for 15. If he had bought 2 more apples and 3 fewer oranges, he would have spent 13. We need to find the price of one apple and one orange.
2. **Define variables:** Let the price of one apple be $a$ and the price of one orange be $b$.
Let the original number of apples bought be $x$ and the number of oranges be $y$.
3. **Write equations from the problem:**
- The cost for $x$ apples and $y$ oranges is 15:
$$a x + b y = 15$$
- The cost for $(x+2)$ apples and $(y-3)$ oranges is 13:
$$a(x+2) + b(y-3) = 13$$
4. **Expand second equation:**
$$a x + 2a + b y - 3b = 13$$
5. **Subtract the first equation from the expanded second equation:**
$$(a x + 2a + b y - 3b) - (a x + b y) = 13 - 15$$
$$2a - 3b = -2$$
6. **Simplify:**
$$2a - 3b = -2$$
7. **Express one variable in terms of the other:**
$$2a = 3b - 2$$
$$a = \frac{3b - 2}{2}$$
8. **Substitute $a$ into the first equation:**
$$a x + b y = 15$$
$$\left(\frac{3b - 2}{2}\right) x + b y = 15$$
9. **Note:** We have two equations but four variables: $a,b,x,y$. We need more information or constraints to solve uniquely. Usually, number of fruits bought ($x,y$) is a positive integer.
10. **Assume $x,y$ are integers and prices are positive. Solve the system:
We have:**
- $$a x + b y = 15$$
- $$2a - 3b = -2$$
11. **Try integer values for $x$ and $y$ to find integer $a$ and $b$: For example, solve for $a$ and $b$ given $x=3$ and $y=3$:**
- Substituting $x=3,y=3$ in $a x + b y=15$:
$$3a + 3b = 15$$
$$a + b = 5$$
- From earlier, $$2a - 3b = -2$$
12. **Solve these two equations:**
- $$a + b = 5$$
- $$2a - 3b = -2$$
Multiply the first by 3:
$$3a + 3b = 15$$
Add this to the second:
$$2a - 3b = -2$$
$$3a + 3b = 15$$
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$$5a = 13$$
$$a = \frac{13}{5} = 2.6$$
Substitute back for $b$:
$$2.6 + b = 5 \,\Rightarrow\, b = 2.4$$
Prices are $a=2.6$ and $b=2.4$.
13. **Verification:**
- Original cost: $3 \times 2.6 + 3 \times 2.4 = 7.8 + 7.2 = 15$
- New cost: $(3+2) \times 2.6 + (3-3) \times 2.4 = 5 \times 2.6 + 0 = 13$
This satisfies both conditions.
**Final answer:** The price of an apple is $\boxed{2.6}$ and the price of an orange is $\boxed{2.4}$.