Answer:
2x + y = 17
-6x = 3y - 51
Explanation:
You get an infinite number of solutions when two equations are really just the same. This means you can convert one into the other simply by multiplying one to get the other.
In the above answer, if you multiply the above by -3 you get:
-6x -3y = -51
which is of course -6x = 3y - 51
So that is an example of a pair that has infinite solutions.
To find all of them, you'd carefully have to compare each 2 and see if there is a multiplier to convert one into the other. You can do that!