Rodney sold a total of $175 / $25 = 7 security systems.
Let's assume the number of security systems he sold on the second street is x.
The first street sold half as many as the second street, so the first street sold x / 2 security systems.
The third street turned him away, so he sold 0 security systems on the third street.
The fourth street resulted in only one sale, so he sold 1 security system on the fourth street.
In total, Rodney sold x + x / 2 + 0 + 1 = 7 security systems.
Combining like terms, we get 1.5x + 1 = 7.
Subtracting 1 from both sides, we get 1.5x = 6.
Dividing both sides by 1.5, we get x = 4.
Therefore, Rodney sold 4 security systems on the second street.
#### 4
The answer is: 4
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
Rodney is a door-to-door salesman trying to sell home security systems. He gets a commission of $25 for each system he sells. He is canvassing a neighborhood of four streets with eight houses each. The first street gave him half the sales that the second street did, while every house on the third street turned him away and the fourth street resulted in only one sale. His total commission was $175. How many security systems did he sell on the second street?

### Answer:
