They want you to find the composite function and they evaluate it at a give value for x...first the composite function...
f(g(x))=(x-1.5)^2+3(x-1.5)+6
f(g(x))=x^2-3x+2.25+3x-4.5+6
f(g(x))=x^2+3.75, this is the completed composition function...now:
f(g(1)=1+3.75=4.75