a) ( a - 64 : 8 + 6 * 4 ) : 5 = 5
a - 64 : 8 + 6 * 4 = 5*5
a - 64 : 8 + 6*4 = 25
6 * 4 = 24 : 64 : 8 = 8
a - 8 + 24 = 25
a - 8 = 25 -24
a = 1 + 8
a = 9
b) ( 9 - 64 : 8 + 6 * b) : 5 = 5
9 - 64 : 8 + 6 *b = 25
9 - 8 + 6*b = 25
1 + 6b = 25
6b = 25 -1
6b = 24
b = 24 : 6
b = 4