Answer:
x = (c+a)/2
y = (c-a)/2
Explanation:
x+y=c
x-y=a
Add together to eliminate y
x+y=c
x-y=a
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2x = c+a
Divide by 2
2x/2 =(c+a)/2
x = (c+a)/2
Multiply the second equation by -1
-x+y =-a
Add the first equation
x+y =c
-x+y=-a
-----------------
2y = c-a
Divide by 2
2y/2= (c-a)/2
y = (c-a)/2