Solving an Equation with given variables

I'm learning matlab and trying to set up an code to solve an equation with given inputs, where those inputs might not be for the same variable every time. e.g. f = x + y sometimes you have x and y, other times you have f and x, etc.

Right now I'm just trying to get the solve function to work, I can worry about input prompts later.

clc
syms f x y
f = 5;
x=2;
f == x + y;
S = solve(f,y)

I'm getting a return of an empty matrix.

S =
Empty sym: 0-by-1

The tutorial tells me it's because the solution doesn't exist. Obviously the solution is y=3.

Thank you for your assistance!

Answer 1

[Walter Roberson]

f == x + y;

is not an assignment statement.

eqn = f == x + y;
S = solve(eqn, y)