Answer:
-6x + 2
Step-by-step explanation:
Let the number that should be added to 3x + 4x - 7 be y.
[tex]\rm3x+4x-7+y=x-5[/tex]
[tex]\rm y = (x-5) - (3x+4x-7)[/tex]
[tex]\rm y = x - 5 - 3x - 4x + 7[/tex]
[tex]\boxed{\rm{y=-6x+2}}[/tex]
#CarryOnLearning