As per question,
Brand $$X$$ sunscreen cost $$=Rs.\ 70$$
And with sales tax$$=Rs.\ 75$$
Now, sales tax paid $$=Rs.\ 75-Rs.\ 70=Rs.\ 5$$
Again,
Brand $$Y$$ sunscreen cost $$=Rs.\ 62$$
And with sales tax$$=Rs.\ 65$$
Now, sales tax paid $$=Rs.\ 65-Rs.\ 62=Rs.\ 3$$
So, great sales tax rate $$=$$Brand $$X$$
Now, sales tax for brand $$X=\dfrac{5}{70} \times 100=7.14 \%$$
Now, sales tax for brand $$Y=\dfrac{3}{62} \times 100=4.84 \%$$