This claim is proven by building a bijection by following a diagonal procedure.
Imagine you have an infinite matrix, whose coefficient are all possible fractions:
Now, count them "diagonally": this is how we map every natural number, using the same positions:
The attached image, taken from aminsaied.wordpress.com/2012/05/21/diagonal-arguments/, should make it clearer
So this is an equation.
The starting value is the given value 400.
She gave g packs to the orphanage, so she now has 400-g packages.
Then she divides that by 4 and gives to 4 different charities.
The answer is (400-g)÷4
Hope this helps!
A I think but I’m not 100% sure
Volume 48
6x 8y
Multiple 6 times 8