If A = 296 ± 4, and B= 535 ± 4, C=AB-200B, determine C and its % error.

Answer 1

If DA is the uncertainty of A,

(1)
If X = AB or X = A/B, then DX/X = √{(DA/A)2 + (DB/B)2}

(2)
If X = A + B or X = A – B , then: DX = √{(DA)2 + (DB)2}

Plug in your numbers and chug away.

Use formula 1 to get the error in AB
Use formula 2 to get the uncertainty in (AB) - (200B)

a web search on "combining experimental error" will give a good article on this topic.