how to print letters and variable in edittext at the same time? PLEASE

I want that in the edittext print the text y = x where "x" was previously calculated and in this case to put an example is "2x" I want edidtext to print "y = 2x" because my program looks for the equation of a line, good the equation of the tangent line to a point on a curve How can I print variables and letters in edidtext at the same time?

syms x z f=get(handles.edit1,'string'); fs=sym(f); df=diff(fs); e=str2double(get(handles.edit10,'string')); y1=str2double(get(handles.edit11,'string')); m=subs(df,x,e); y=char(m*x-m*e+y1); set(handles.edit12,'string','y=y'dd');

[Karan Gill]

Can you format your code? Also, what line in your code are you referring to?