n:  round to the n-th digit after "."   (if n=2 to cents; if n=0 to integers; if n=−2 to hundreds; ...)
 

a·x = b     n =  
a =   b =   x =
 
a/x = b     n =  
a =   b =   x =
 
a·x²+b·x+c = 0    n =       b²−4ac -b/(2a)
a =   b =   c =
x1 =   x2 =
 
a^x = b     n =  
a =   b =   x =
 
x^a = b     n =  
a =   b =   x =
 
a·x³ + b·x² + c·x + d = 0     n =  
a =   b =   c =   d =
x1 =   x2 =   x3 =
 
a·x⁴ + b·x³ + c·x² + d·x + e = 0     n =  
a =   b =   c =   d =   e =
x1 =   x2 =   x3 =   x4 =
 

If you have to put a coefficient using some function symbol (for example 1/5, √2), put it in a numerical form (0.2, 1.414213562373095), for example using this
NOTES