Explanation:
1. The best way to solve this one would be elimination
Both the equations have the same term, 5y
Since neither variable is isolated, it wouldn't be easy to use the method of substitution
2. Both the equations only have x or y
SInce neither of the equations has both the variables, substitution is impossible
3. Same as 1, just that you would need to multiple one of the equations by a certain number to create equal terms to make elimination possible
4. It's perfect!!! The y is isolated and it would be simple to just substitute the first equation into the 2nd (I hope you got what I meant)
4, is the correct answer
I hope this helps!!!