Answer:
The answer is A.
Step-by-step explanation:
So we have the two equations:
[tex]3x+y=1\\y+4=5x[/tex]
To make a substitution of the second equation into the first equation, we need to isolate the y variable in the second equation. Thus:
[tex]y+4=5x\\y=5x-4[/tex]
Now, we can substitute this into the first equation. Therefore:
[tex]3x+y=1\\3x+(5x-4)=1\\3x+5x-4=1[/tex]