Answer:
a = 24
b = 10
c = 26
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Step-by-step explanation:
We're given a list of possible b values and they are:
4, 5, 8, 10, 12, 24
Let's make a table to show what each value of 'a' would be based on those b values above.

Example calculation: If b = 4, then a = 2b+4 = 2*4+4 = 12 (first row)
I recommend using spreadsheet software to quickly compute these values. Also, a spreadsheet is useful to organize the data into a table.
Next we'll add a third column c.
This column will be computed using the formula
which is based from the pythagorean theorem

So,

Each decimal value mentioned is approximate. The only time c is an integer is when a = 24 and b = 10.
So that's how I got a = 24, b = 10, c = 26 as the final answer.