The functions f(x) and g(x) are defined below for x> 5
f(x)=(x-5)2
g(x)=x+the square root of x -3

(gof)(x) means g composed with f or g(f(x))

so
(gof)(20)=g(f(20))
evaluate f(20) then plug that value in for x in g(x)

f(20)=(20-5)^2
f(20)=(15)^2
f(20)=225

now input that for x in g(x)

g(225)=225+
g(225)=225+ 15-3
g(225)=237
(gof)(20)=237