Solve for specific variable - like Excel's solver

I would like to determine the value of a variable within a complex equation. For example, let's say my equation is y = mx + b. This is simplified but still useful. I know what y is, but I don't know what x is. I want to determine which value of x gives the known value of y. As another example, I am trying to tell MATLAB how to act like the Excel Solver add-in.

I have tried to follow various guides online and used simple equations as outlined below. I encounter the same error and I'm not sure what else I might try. How might I go about this process?

My example code and the corresponding error follows:

>> syms x;

t = solve('2*x+6==0', 'x');

Error using solve>getEqns (line 418)

List of equations must not be empty.

Error in solve (line 226)

[eqns,vars,options] = getEqns(varargin{:});

Answer 1

[Star Strider]

The problem is with the single (or any other) quotes.

Remove them, and then:

syms x
t = solve(2*x+6==0, x)

produces:

t =  
-3

.

[Aaron Ashley]

Thanks! That resolved the issue.

[Star Strider]

As always, my pleasure!