if the needed amount is z, then
x/y + z = y/x
z = y/x - x/y
You can massage that into other forms if you like.
Not sure why this caused you trouble. If I ask what needs to be added to 6 to make 10, you naturally say
10-6 = 4
right?
What must be added to x/y to make it y/x??
1 answer