48.sagews

var('a b c')
d0 = {a:1,b:2,c:x}
d1 = dict(a = 1,b = 2,c = x)
(a.subs(d0) + b == c).subs(d0);(a.subs(d1) + b == c).subs(d1)

3 == x b + 1 == c

d0;d1

{a: 1, c: x, b: 2} {'a': 1, 'c': x, 'b': 2}