b=a+x, for a

Subtract x from both sides of the equation.

That will leave you with an equation for a.

I still don't understand

Is it b-x=a

Yes, but you might want to write it as

a = b-x
which is the same thing.

The variable you want to know the value of (a, in this case) usually is put on the left.

Thanks

To solve the equation b = a + x for a, you need to isolate a on one side of the equation. Let's break down the steps to do that:

1. Start with the original equation: b = a + x.
2. Subtract x from both sides of the equation to move it to the other side: b - x = a + x - x.
3. Simplify the equation: b - x = a.
4. So the equation b = a + x is equivalent to a = b - x.

Therefore, the value of a can be obtained by subtracting x from b.