Answer: x plus y equals 28. x equals 3 y.
Explanation:
The equation can be written as
x+y=28
x=3y
x is already partially solved here, so you could substitute it into the first equation to solve for y.
3y+y=28
4y=28
y=7 We have y, so substitute that in the second equation to solve for x.
x=3(7)
x=21
We now know that x=21 and y=7
Substitute the values into the first equation:
21+7=28
28=28
So that system of equations is correct.