Complete the blanks so that both sides of the equation are equal.
 
(a) 239 \(+\) \(=\) 280 \(+\) 24
 
(b) 133 \(-\) 51 \(=\) 147 \(-\)
 
(c) 96 \(+\) 33 \(=\) 166 \(-\)