Can anyone help me with this math problem? Im doing Algebraic Equations?

Question

x+y=4
x-y=8.5

Answer 1

x+y=4
x-y=8.5

Just add the 2 equations

it will result to this one:

2x-0y=12.5
2x=12.5
x=6.25

using x, we could get the value of y.just choose from the 2 given equations where you could substitute x.

x+y=4
6.25+y=4
y= -2.25

Answer 2

First add the two equations:

2x = 12.5 and then x= 6.25

Now put x in first equation:

6.25 + y =4, and y = 4 -6.25 = -2.25