C.
Explanation:
x + y = 10
x - y = 4
x = 4 + y
Okay, so now we substitute our third equation into equation 1. Then equation one becomes..
4 + y + y = 10
4 + 2y = 10 ┌(・。・)┘♪
Mk now we subtract 4 from both sides ofc.
2y = 10 - 4
2y = 6
Now divide by 2
y = 3
And now the last one-
substituting y = 3 into equation 3 to find the value of x!
(. ❛ ᴗ ❛.)
x = 4 + y, x = 4 + 3, x = 7
So, that's how I got this answer! (◕ᴗ◕✿)