Explanation:
x+y=180
x=180-y------(i)
x-y=70------(ii)
Now,
Putting the value of x in equation (ii)
x-y=70
(180-y)-y=70
180+2y=70
2y=70-180
2y= - 110
y= - 110/2
y= - 55
Again,
x=180-(-55)
x=235
x-(-55)=70
x+55=70
x=70-55
x=15
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