Answer:
square root of 81
Step-by-step explanation:

so 9 is rational number.
the rest are irrational number
A. 25 = (.5 * 22) + (2 * x)
B. 25 = (.5 * 22) + (2 * x)
25 = 11 + 2x
14 = 2x
7 = x
C. 7
Your method is right so u already know how to do it
You can calculate it using the law of cosines: c^2=a^2+b^2-2*a*b*cos(C)
your triangle is
CD=15=a
CE=?=b
DE=CE+3=b+3=c
and C=90°
-> insert those values, with c substituted with b+3 to remove c
c^2=a^2+b^2-2*a*b*cos(C)
(b+3)^2=15^2+b^2-2*15*b*cos(90)
cos(90)=0->
(b+3)^2=15^2+b^2
b^2+2*3*b+3^2=225+b^2
6b+9=225
6b=216
b=36=CE
DE=CE+3=36+3=39