Not familiar with the SHT11, but at a glance I can say the PIC will not work with decimals or negatives. However. if you wanted to add -46.85 + 175.72 it could be structured

(17572 - 4685) / 100

Multiplication works similarly; Var * 1.75 becomes (Var * 175) / 100.

Something tells me I'm not even getting close to the jist of your question. If you can elaborate some, I'll see if I can help.