Latest versions are more exhaustive in the error description; I get a "Data - not defined"... looking at the code I see there is a uppercase typo in the definition of X.
![2016-07-24 22_55_52-SMath Studio Desktop - [Maths%20Error%200.207511520256057.sm_].png](/en-US/file/YvV4Nm/2016-07-24-22_55_52-SMath-Studio-Desktop---_Maths_20Error_200_207511520256057_sm___png)
![2016-07-24 23_06_11-SMath Studio Desktop - [Maths%20Error%200.207511520256057.sm_].png](/en-US/file/xMBsUK/2016-07-24-23_06_11-SMath-Studio-Desktop---_Maths_20Error_200_207511520256057_sm___png)
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