a) (m+n)-(n+p)-(m+p)=> m + n - n - p - m - p=> m - m - p - p=> -2p
b) (a+b-c)+(a-b+c)-(a-b-c)=> a + b - c + a - b + c - a + b - c=> 2b - 2c
a) (m+n)-(n+p)-(m+p)
=> m + n - n - p - m - p
=> m - m - p - p
=> -2p
b) (a+b-c)+(a-b+c)-(a-b-c)
=> a + b - c + a - b + c - a + b - c
=> 2b - 2c