Jennifer M. answered  08/26/19
Experienced AP and College Calculus and Physics Tutor
An equation with infinite solutions is when the left hand side equals the right hand side, so that when combining like terms you end up with 0 = 0.
Since they want 3x + 6 on the left hand side, a simple answer would be:
3x + 6 = 3x + 6
Or, you could make it look a little more complicated:
3x + 6 = 2x + x + 5 + 1
As long as the left hand side equals the right hand side, there will be infinite solutions.
Hope this helps!