reworked question, same worksheet in cocalc.

this is my code:

```
g=solve(e_Ersatz/(2*d_k)==e_s/d_e, d_k)
print g
show(g[0].subs({
d_e: RIF(.999,1.001),
d_m: RIF(.25,.1),
e_m: e_0 * RIF(80.5,81.5),
e_s: e_0 * RIF(3,4)
}))
f=g[0].subs({
d_e: RIF(.999,1.001),
d_m: RIF(.25,.1),
e_m: e_0 * RIF(80.5,81.5),
e_s: e_0 * RIF(3,4)
})
#show( n(f) )
```

this is g:

```
[
d_k == (d_e*d_m*e_m - (d_e*d_m + 2*d_m^2)*e_s)/(d_e*e_m - 2*d_m*e_s)
]
```

So its not really complicated, a little summation, some factors, a square. Nothing I could not do manually, even with the error propagtion.

But when trying to get the RIF ~~range not reflected in (half)numeric output ~~

equvalent I get ```
*** WARNING: Code contains possible implicit multiplication ***
*** Check if any of [ 5e, 5e ] need a "*" sign for multiplication, e.g. 5x should be 5*x ! ***
Error in lines 82-82
Traceback (most recent call last):
File "/cocalc/lib/python2.7/site-packages/smc_sagews/sage_server.py", line 1188, in execute
flags=compile_flags) in namespace, locals
File "", line 1, in <module>
File "/ext/sage/sage-8.6_1804/local/lib/python2.7/site-packages/sage/misc/functional.py", line 1419, in numerical_approx
return n(prec, algorithm=algorithm)
File "sage/symbolic/expression.pyx", line 5981, in sage.symbolic.expression.Expression.numerical_approx (build/cythonized/sage/symbolic/expression.cpp:34636)
raise TypeError("cannot evaluate symbolic expression numerically")
TypeError: cannot evaluate symbolic expression numerically
```

Hu? Am I missing something fundamental? Is this a bug?

================
old question:

This is my worksheet:
https://cocalc.com/share/f7766c5e-2f4d-4916-bb0d-74a7182e5fd5/2019-02-09-203517.sagews?viewer=share

I have an equation that I insert some numeric values into. Because I need to estimate the range of uncertainty, I specify the values as RIF numbers:

```
d[0].subs(
d_e == RIF(.999,1.001),
x ==.25,
d_m == RIF(.05,.15),
U == RIF(10^-9,1.02*10^-9),
e_m == e_0 * RIF(80.5,81.5),
e_s == e_0 * RIF(3,4)
)
```

However, in the output that range is not expressed. Is that becaues there are remaining symbolic ~~parameters? ~~parameters?