Cross multiply: 3(a+2)=b(a+5)
Simplify: 3a+6=ab+5b
Isolate the constant: 3a−ab−5b=−6
Factor out a: a(3−b)−5b=−6
Add 15 to both sides: a(3−b)−5b+15=9
Factor out b: a(3−b)+5(3−b)=9
Combine like terms: (a+5)(3−b)=9
Note that a+5 must equal 1, 3, or 9, so 3−b can equal the other factor of 9.
Thus, there are 3 cases that work.
Note that the cases are (4, 2), (-2, 0), and (-4, -6)