Let's break down the problem step by step to understand how many US dollars Mitchell has remaining after going through the given transactions.
1. Exchange 150 US dollars to Canadian dollars
Mitchell starts with 150 US dollars. The exchange rate from USD to Canadian dollars is 0.97071 per USD.
[tex]\[
\text{Canadian dollars received} = 150 \, \text{USD} \times 0.97071 \, \left(\text{CAD per USD}\right) = 145.6065 \, \text{CAD}
\][/tex]
2. Spending 20 Canadian dollars
After receiving 145.6065 Canadian dollars, Mitchell spends 20 of those Canadian dollars.
[tex]\[
\text{Canadian dollars remaining} = 145.6065 \, \text{CAD} - 20 \, \text{CAD} = 125.6065 \, \text{CAD}
\][/tex]
3. Exchange the remaining Canadian dollars back to US dollars
Now, Mitchell has 125.6065 Canadian dollars remaining. The exchange rate from Canadian dollars to US dollars is 1.03069 per CAD.
[tex]\[
\text{US dollars remaining} = 125.6065 \, \text{CAD} \times 1.03069 \, \left(\text{USD per CAD}\right) = 129.4614 \, \text{USD}
\][/tex]
From the computations, Mitchell has approximately 129.46 US dollars remaining after all transactions.
Therefore, the correct answer is:
[tex]\[ \boxed{129.46} \][/tex]
