step 1) turn 1.9 into an improper fraction.
= 19/10
step 2) find a least common denominator between 10 and 12.
= 60
(10x6 and 12x5)
step 3) convert the fractions so they have the same denominator.
= 19x6 is 114.
10x6= 60.
= 11x5 is 55.
12x5 is 60.
now you have your new fractions.
step 4) subtract.
= 114/60 - 55/60 is 59/60.
step 5) simplify.
the answer is either 0.9833... (3 repeating) or just 59/60 (you can't simplify the fraction any further).