Can u guys answer these 2 questions pls

14)  answer is 4

15) proved

Step-by-step explanation:

x=7-4√3 , √x +1/√x

√(7-4√3) +1/√7-4√3)=

8-4√x/√(7-4√3)= 4 ( use calculator)

(81/16)^-3/4*[(25/9)^-3/2 ÷(5/2)^-3]=(81/16)^-3/4= (9²/4²)^-3/4=(4^6/4)/(9^6/4)=8/(27)=8/27(25/9)^-3/2= (9^(3/2))/(25^3/2)=27/125(5/2)^-3=2³/5³ =8/125put the number to find the result:8/27[(27/125)÷(8/125)=8/27[(27/125)×125/8)]=    125 in nominator and dinaminotor=18/27[27/8]=1 proved