Răspuns :
( 7·9 - 5x ) - 9:3 = 20
( 63 - 5x ) - 3 = 20
63 - 5x = 23
5x = 40
x = 8
( 63 - 5x ) - 3 = 20
63 - 5x = 23
5x = 40
x = 8
( 63 - 5x ) - 3 = 20
63 - 5x = 20 + 3
63 - 5x = 23
5x = 63 - 23
5x = 40
x = 40 : 5
x = 8
63 - 5x = 20 + 3
63 - 5x = 23
5x = 63 - 23
5x = 40
x = 40 : 5
x = 8