Answer:
9 or -6
Explanation:
To solve, I would suggest factoring.
You need to find two numbers which can be multiplied for 54 and also combined in some way to get 3. In this case, 9 and 6 are perfect.
![x^2-3x-54=0\\(x-9)(x+6)=0](https://img.qammunity.org/2020/formulas/mathematics/middle-school/61t3xdhuc3qdwru0uy68k6fdmqzjvzbgdl.png)
Next, you can set both of your terms equal to zero to find your possible solutions.
![x-9=0\\x=9\\](https://img.qammunity.org/2020/formulas/mathematics/middle-school/o2lppgecbu6onv8d1vxgu0hsz18ihly14a.png)
or
![x+6=0\\x=-6](https://img.qammunity.org/2020/formulas/mathematics/middle-school/e2zjci6ncc7cf4jkk74q50ilou0mmy4mr7.png)