Answer:
A = 10
Explanation:
Use formula: c = sqrt of a^2 + b^2
1) Put in known numbers:
26 = sqrt of a^2 + 24^2
But instead of adding you would subtract and rearrange the formula bc you already have C: 
2) Solve: 
A = sqrt of 26^2 - 24^2
A = sqrt of 676 - 576
A = sqrt of 100
A = 10
Sqrt: square root 
Therefore, out answer… I hope this helps! Best of Luck! (\^ v ^/)