Subtraction problems has slerger integers show first

[CCecilia]

Describe the bug
Currently when subtraction problems are generated a larger int can be the first number in the problem. This is unintended as the answers are expected to be positive integers.

To Reproduce
Steps to reproduce the behavior:

1. run math-test --problems 10 --subtraction --no-addition
2. output Problem: 1 - 9 = ?
3. input 8
   4.test results

INCORRECT
User Answer: 1 - 9 = 8
Expected: 1 - 9 = 4294967288

Expected behavior
A clear and concise description of what you expected to happen.

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Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Additional context
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