If you can manipulate the two equations so that they have exactly the same coefficients (e. g., 3x + 4y = 8 and 2x + 4y = 8), then you conclude that the two lines coincide (overlap), and that there are thus infinitely many solutions.
Answer:

Step-by-step explanation:

For Ava if It’s 11 months and for mark it is 15 months and the number is 1,650! (I spent time doing this, and I did. Calculation to make sure you would get this right!)
Answer:
2, 6, and 7
Step-by-step explanation:
3n is by itself because theres no other numbers that have the letter n.
6m and -11m are like terms bcs they both have the letter m (variable)
-3 and -18 are both like terms bcs they are both just numbers (or constants whatever)
so you would choose options 2, 6, and 7! hope this helps! :)