How can you tell if (4,7) is a solution

In order to check if the x and y value is a solution then you need to plug in your numbers for the x and why value.

Take this as an example with your solution (4,7) let's try 4x-9=y. We want to plug in the values of each variable so the new equation will look like 4 (4) - 9 = (7). Now you want to multiply and get 16-9=7 next subtract and you get 7=7. This would be a solution for the problem.

Now we can try 3x+14=y do the same thing from last example and you'll get 3 (4) - 14=7 and now multiply to get 12-14=7 now subtract and you'll get - 2=7 which is NOT a solution to this equation so it would become - 2≠7.

you have to plug it into your equation