By selling his cow at Sh. 34,000, Obula made a loss of 15%. At what price had he bought the cow?

A loss of 15% means the selling price is $100\% - 15\% = 85\%$ of the cost price.
So, $\text{Selling Price} = 0.85 \times \text{Cost Price}$.

We know the selling price is sh. 34000.

Divide the selling price by 0.85.

The price at which Obala had bought the cow was $\text{sh. } 40000$.