The task is to find a double digit number which is 19 times greater than it's second digit

I made an equation which looked like this: 10a+b=19b (a is the first digit and b is the second one)

but there are two unknown values(a,b) so i need another equation but how would it look like because i cant think of any way i can make it.

The answer is easy to figure out because its just a double digit but how would i prove that i am not guessing. The answer is 95.

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