Răspuns :
( 9 x9 - m - 8 x4 ) : 7 = 2 x2
81 - m - 32 = 2 x2 x 7
81 - m - 32 = 28
49 - m = 28
49 - 28 = m
21 = m
m = 21
81 - m - 32 = 2 x2 x 7
81 - m - 32 = 28
49 - m = 28
49 - 28 = m
21 = m
m = 21