Răspuns :
28 + 15 : a + 7 = 38
35 + 15 : a = 38
15 : a = 38 - 35
15 : a = 3
a = 15: 3
a = 5
28 + 15 : 5 + 21:3 = 28 + 3 + 7 = 38
35 + 15 : a = 38
15 : a = 38 - 35
15 : a = 3
a = 15: 3
a = 5
28 + 15 : 5 + 21:3 = 28 + 3 + 7 = 38