How do you write 8 21/40 as a decimal

to write 8 21/40 as a decimal we need to write the fraction where denominator is a power of 10.
the denominator now is 40, when we multiply 40 by 25, we get 1000.
then the denominator would be a power of 10.
                                                                     
lets multiply the fraction 21/40 by 25 
 8 21/40 is a mixed fraction made of 8 wholes and a fraction that is now 525/1000.
                                                                   
when dividing by 1000, the decimal point that is after 525 should move 3 decimal places to the left, then the decimal point comes before 525.
then 21/40 is equal to 0.525. since we have 8 wholes;                                                                     8 + 0.525 = 8.525

Ihave, but this question is gonna probably get deleted.