EXPLANATION
Let's see the facts:
Exchange rate = 6 Tala / $5
Applying the unitary method would give us the appropiate relationship:
[tex]\text{Number of Tala=}\frac{6\text{ Tala}}{5\text{usd}}\cdot30\text{usd}[/tex]Multiplying numbers and simplifying:
[tex]\text{Number of Tala= 36 Tala}[/tex]The number of Tala would be 36.