# Sage refuses to evaluate summations...

I'm trying to define a function

```
g(x) = sum(frac(j*p/q), j, 0, x)
```

where `p`

, `q`

are pre-defined constants (say `(p, q)=(33, 21)`

).
Sage did not give any errors, but when I type `g(10)`

,
I would get output symbolic expression `sum(frac(11/7*j), j, 0, 10)`

,
which is different from the expected value `31/7`

.

How do I fix this?