In a school there are w more girls than boys. If there are x girls How many pupils are there in that school?
There are w more girls than boys in the school. Let's denote the number of girls by g, and the number of boys by b. Then we can write:

g - b = w

We know that there are x girls in the school, so we can substitute g = x in the equation above:

x - b = w

Now we can solve for b:

b = x - w

Now we can substitute b back in the original equation and solve for g:

g = b + w

g = (x - w) + w

g = x

Now we know that there are x girls and b boys in the school. We also know that x + b = the total number of pupils in the school. So, the total number of pupils in the school is:

x + b = x + (x - w)

x + b = 2x - w

Now we can substitute x = the number of girls and b = the number of boys:

x + b = 2x - w

x + (x - w) = 2x - w

2x - w = 2x - w
