X- - 3 = 10

what is the value of x?

x = 7

Step-by-step explanation:

Rule: an even number of - signs written one after another produces a plus number.

So - - 3 = 3

The rule also lets you do something strange like

- - - - 4 = 4 but you hardly ever see this.

Rule: an odd number of minus signs produces a minus number.

x + 3 = 10                 Subtract 3 from both sides.

x + 3 - 3 = 10 - 3      

x = 7