Solve this system of equations using substitution (show your work).
x + 3=7
3x+ y=7
Show work
From the first equation, we can solve for x:
x + 3 = 7
x = 7 - 3
x = 4
Now, we substitute this value of x into the second equation to solve for y:
3(4) + y = 7
12 + y = 7
y = 7 - 12
y = -5
Therefore, the solution to the system of equations is x = 4 and y = -5.