[tex]f(x)=x+3;\ g(x)=x^2\\\\(g\circ f)(x)=g(f(x))=(x+3)^2\\\\(g\circ f)(1)-\text{put the value of x=1 to the equation of the function}\\\\(g\circ f)(1)=(1+3)^2=(4)^2=16[/tex]