so here first you have to have same denominators to subtract and add.
to make same denominator you have to multiply something to them which meets up to their lowest common multiple (LCM). so here the easiest thing is multiply each denominator to the other but remember you have to multiply them to the numerator too.
3×9/5×9-2×5/9×5
so it becomes
27/45-10/45
17/45
as you cant bring to its simplest form since the answer in a prime no. leave it like that.
