30,45, x, 100; The median is 51

To solve for x, you must first understand how the median was calculated out of the given set of numbers. Without looking at the given median value, we can see that we cannot get the median by process of elimination since there are an even amount of numbers in this particular set. Therefore, we must average the two closest values to what should be the median.

In this case, the values are "45" and "x". If we pretend that we know the value of the variable "x" (for example we will pretend that x is 55), then we should have an equation that looks like this: (45+55) : 2 = [median]. What this equation is doing is adding the two closest values to the median (45 and 55) and dividing it by 2, the number of values we are averaging. Now we can solve this equation and simplify it to 100 : 2 which is 50, our median.

So if they give us the median instead of the x value, then we can rewrite the equation to fit your request: (45+x) : 2 = 51. Now we can solve for x:

1. Multiply by 2

(45+x) = 102

2. Subtract 45

x = 57

The x value for your question is 57.