Answer:
a) 255
b) 61602
c)
d)
Step-by-step explanation:
You need to understand the decimal equivalent of hexadecimal numbers, from 0 to 9 numbers are represented the same way, from 10 to 15 we use the alphabet, meaning 10 equals A in hexadecimal base, 11-B, 12-C, 13-D, 14-E, and 15-F.
For your first exercise you'll enumerate the number's positions fromright to lef begining with 0:
a. F F
position 1 0
Now you'll multiply your hexadecimal number (using the decimal equivalent for your letters) for the base (16) elevated to the number of the position:

Finally, you'll add your results:
240+15=255
FF=255
b. F 0 A 2
position 3 2 1 0

F0A2=61602
c. F 1 0 0
position 3 2 1 0

0F100=61696
d. 1 0 0
position 2 1 0

100=256
I hope you find this information useful! Good luck!