x = 4; x += 7?

Question

what is the value of x

Answer 1

In C++ and Java, += is the addition assignment operator. It's equivalent to saying:
x = x + 7

Since x started with a value of 4, it will now have a value of 11.

Answer 2

This looks like a part of a script.

at x = 4; x is defined as 4

x += 7 is the same as 'x = x +7', however in maths that's never correct. The meaning of it is, x gets a new value, which is 7 higher than the old value.

The old value was 4, increased by 7.

4+7=11