1 | initial version |

The variable `i`

was overwritten with $2$.

The error can be recovered as follows:

```
sage: var( 'h,i' );
sage: solve( [h+i == 7, h-i == 3], [h,i] )
[[h == 5, i == 2]]
sage: for i in range(3): print "i = %s" % i
i = 0
i = 1
i = 2
sage: solve( [h+i == 7, h-i == 3], [h,i] )
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-628-48574179ae51> in <module>()
----> 1 solve( [h+i == Integer(7), h-i == Integer(3)], [h,i] )
/usr/lib/python2.7/site-packages/sage/symbolic/relation.pyc in solve(f, *args, **kwds)
974 for i in x:
975 if not isinstance(i, Expression):
--> 976 raise TypeError("%s is not a valid variable." % repr(i))
977 elif x is None:
978 vars = f.variables()
TypeError: 2 is not a valid variable.
```

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