Answer:
![3 - a](https://img.qammunity.org/2021/formulas/mathematics/college/ar4e108sval470ywlykqkcr0fb8f6b6owx.png)
Explanation:
Given that when you add two numbers together the result is 3.
The greater of the number is given as a.
Let "x" represent that lesser number.
Thus:
![a + x = 3](https://img.qammunity.org/2021/formulas/mathematics/college/26j83gyjztmmr0s7dc3ig2ua3x272myeiy.png)
To make x the subject of the formula. Subtract a from both x.
![a + x - a = 3 - a](https://img.qammunity.org/2021/formulas/mathematics/college/w7yz9ep0e6v6qb393hfrrnp999jz705pzy.png)
![x = 3 - a](https://img.qammunity.org/2021/formulas/mathematics/college/v8gq3soru7dgvlqaesv4vukrw0gudb8al6.png)
Therefore, the expression that represents the lesser number, x, is:
![3 - a](https://img.qammunity.org/2021/formulas/mathematics/college/ar4e108sval470ywlykqkcr0fb8f6b6owx.png)