Hello!
You use the Pythagorean theorem to solve this
[tex] a^{2} + b^{2} = c^{2} [/tex]
Put in the values it tells you to
[tex]a^{2} + 4.4^{2} = 5.5^{2} [/tex]
Square the numbers
[tex]a^{2} + 19.36 = 30.25[/tex]
Subtract 19.36 from both sides
[tex] a^{2} = 10.89[/tex]
Take the square root of both sides
a = 3.3
The answer is 3.3
Hope this helps!