We want to find the value of $X$ in the given situation.
To determine the average score, we need to find the sum of all four exam scores and divide it by 4.
We are given the scores of the first three exams: 87, 83, and 88.
Let's calculate the sum of these scores:
87 + 83 + 88 = 258
The sum of the first three scores is 258.
To find the average, we divide this sum by 3:
258 / 3 = 86
Now, we want to find the amount by which Kim's average will increase.
Let's calculate her average with the fourth exam score included:
(258 + X) / 4
We are given that the increase in the average is 1, so we can set up the equation:
(258 + X) / 4 - 86 = 1
To solve for $X$, we can multiply both sides of the equation by 4 to eliminate the fraction:
258 + X - 344 = 4
Simplifying, we have:
X - 86 = 4
Adding 86 to both sides of the equation, we find:
X = 90
The value of X is 90.
The answer is: 90
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
Kim earned scores of 87, 83 and 88 on her first three mathematics examinations. If Kim receives a score of X on the fourth exam, then by how much will her average increase?
If we know the answer to the above question is 1, what is the value of unknown variable X?

### Answer:
