Answer is a= 7.75 units squared
Your answer may need to be rounded depending on what your teacher requires
Step by step
Pythagorean theorem
a^2 + b^2 = c^2
a^2 + 2^2 = 8^2
a^2 + 4 = 64
Subtract 4 from each side
a^2 + 4 - 4 = 64 - 4
a^2 = 60
Take the square root of both side
a= 7.75 units