Marks obtained by a boy in Hindi out of $$80 = 60$$ marks
So, his percentage in Hindi $$= \dfrac{60 }{ 80} \times 100 = 600 / 8$$
$$= 75\%$$
Marks obtained by a boy in English out of $$100 = 75$$
So, his percentage in English $$= \dfrac{75 }{ 100} \times 100 = 75\%$$
Marks scored by a boy in Arithmetic out of $$70 = 65$$
So, his percentage in Arithmetic $$= \dfrac{65 }{ 70} \times 100 = 650 / 7$$
$$=92\dfrac{6}{7}\%$$
Clearly, it shows that he gets best marks in Arithmetic
Now,
Total marks of all the three subjects $$= 80 + 100 + 70$$
$$= 250$$ marks
Total marks obtained by a boy in all the three subjects $$= 60 + 75 + 60$$
$$= 200$$ marks
His overall percentage $$= \dfrac{200 }{ 250} \times 100 = 2000 / 25$$
$$= 80\%$$
Hence, the overall percentage of a boy is $$80\%$$