I think this is correct, Answer is 21
Explanation:
Step 1: Write down formula:
Step 2: Plug in b and c value in formula:
Step 3: Solve the exponents:
![a^2+400=841](https://img.qammunity.org/2022/formulas/mathematics/college/v5vkviu55rbqaps4u0p85nu1tmq6rb9iru.png)
Step 4: Subtract 400 from both sides:
![-400](https://img.qammunity.org/2022/formulas/mathematics/high-school/ee6fvns495a5t74otdd9cdofjikriqojhz.png)
![a^2=441](https://img.qammunity.org/2022/formulas/mathematics/college/y1xo728mymvgymbrrylswrhyi9g7xgps6c.png)
Step 5: Square root both sides:
![√(a^2)=√(441)](https://img.qammunity.org/2022/formulas/mathematics/college/h9jinbwckibz6g035tcrl9naiouhoma2kd.png)
![a=21](https://img.qammunity.org/2022/formulas/mathematics/college/uwnd0bazydfob2m2zuxg5cz6yz7sb0fdvs.png)
Step 6: 29+21: 50
Step 7: 50-29: 21