setting up:
#\color(steelblue)(f(x)=3x-2)# and #\color(indianred)(g(x)=5x+7)#
therefore #2\color(steelblue)(f(x))+\color(indianred)(g(x))# becomes
#2[\color(steelblue)(3x-2)]+[\color(indianred)(5x+7)]#
solving:
#\color(seagreen)(2(3x-2))+5x+7# distribute colored part
#\color(seagreen)(2(3x)+2(-2))+5x+7#
#\color(seagreen)(6x+(-4))+5x+7# simplify
#6x-4+5x+7#
#\color(olive)(6x)\color(teal)(-4)\color(olive)(+5x)\color(teal)(+7)# identify like terms
#\color(olive)(6x+5x)\color(teal)(-4+7)#
#\color(olive)(11x)\color(teal)(+3)# combine like terms
answer: #11x+3#