Step 3 is wrong because when dividing exponents you subtract them x^-10 would be multiplying by x^-12 making it x^-10-12 and that would be x^-22 same applies for the y exponents
Start by proving to them that the number 0.57 can be converted into a fraction . A whole number can't exactly be put in to a fraction. 0.57 can be converted to 14.25/25. This information means that 0.57 IS a rational number. Hope this convinced them!