Evaluate the expression 16a squared-4b when a equals 1/4 and b equals 6

I'm giving two answer because I'm unclear as to what you mean.

For Example: if you meant (16a)² minus 4b then my answer would be:  
#1.  When a=1/4 and b=6  (16a)² minus 4b = (16 times 1/4)² minus 24.
Now, (16 and 1/4)² cancel to 4² which equals 16.  16 minus 24 = -8.

#2.  If you meant 16 times (1/4)² minus 24 then that changes everything! :)
then it would be: 16 times 1/16 minus 24 = 1 minus 24 = -23.

So either -8 or -23 is my answer.

sorry if it's confusing. I'm new at this.  And I hope I didn't make any mistakes.

25 is obviously the correct answer