Find the missing numbers for each of the following problems without doing any calculating.
a) 63 - 63 + = 37 - 37 + 91
b) 59 + 72 - 59 = 89 + - 89
c) 7 + 34 + 48 - 34 = 48 +
d) 24 + 37 - 24 = 37 + 9 - 9 +
e) 42 + 59 - 42 = 55 + 12 - 12 +
