Solve three equations with three unknowns Solve the system:
$$\begin{cases}a+b+c=6\\ab+ac+bc=11\\abc=6\end{cases}$$
The solution is:
$a=1,b=2,c=3$
How can I solve it?

You should post your attempts at the question.
Try rearranging some things to fit them together.
$$\begin{cases}a+b+c=6\\ab+ac+bc=11\\abc=6\end{cases}$$

$$a+b+c=6$$
$$a+c=6-b$$

$$ab+ac+bc=11$$
$$b(a+c)+ac=11$$

$$b(a+c)+ac=11=b(6-b)+ac=11$$
$$ac=\frac{6}{b}$$
$$b(6-b)+ac=11=b(6-b)+\frac{6}{b}=11$$
now you have an equation dependent only upon b.
Rearrange it to find b.  Then substitute the answer for b into the other equations and rearrange and substitute to solve for a or c.  Then substitute that in with b and you can find whichever variable is left.
