Răspuns:
1. 30 = a + a + a
a = 30 : 3
a = 10
2. x + x = x + 8
x = 8
8 + 8 = 8 + 8
16 = 16
3. 7 - c = c + 1
c = 3
7 - 3 = 3 + 1
4 = 4
4. 5 - b = b + 1
b = 2
5 - 2 = 2 + 1
3 = 3
5. m + m = m
m = 0
6. x • x = x + x
x = 2
2 • 2 = 2 + 2
4 = 4
7. 2 • c = c + 5
c = 5
2 • 5 = 5 + 5
10 = 10