Answer is **220**

By solving the equation, we got to know each no. assigned to a new value like 100, 999, and 879:

1-3+4=2

2=100 --> (A)

4-6+9=7

7=999 --> (B)

2-6+7=3

3=879 --> (C)

3-3+6=6, but we don't have the value of 6.

To find 6 value, Using (A), (B), and (C) equation;

**6=2+7-3=100+999-879=220**

**So 3-3+6 = 6 = 220**.

**I preferred to use this way, so that I could use all three (A), (B) & (C) equations.**

The other way is:

6 = 2+2+2 = 100+100+100 = 300.

Similarly there are many ways.