D.8
A and C are out because they would get you ether lower or equal to 20, which is equal to AC and your trying to find X in AB which is so posed to be the what equals AC+BC.
AB=AC+BC
5x=20+BC
5(8)=20+BC
40=20+BC
40=20+20
AC equals 20. AB will have to equal AC+ CB. If you put in A.4 in AB 5X you will get twenty and that not what you want. You want to get a number that will get you the an answer greater to AC. So 5(8)=40.
The value of 3 would be 3,000.
Why thousands? Well because u have to count from the right, then back, so ones, tens, hundreds, then thousands lands on 3 so hope this helps.
A natural number is a positive integer, example, 1,2,5,299 etc.
A rational number is a number that can be expressed as a fraction of integers, such as 245/127, 1/2, 5/1,8/1,...
Since a natural number can be expressed as a fraction of integers, so
a natural number IS a rational number.
I believe it is context clues. The reader typically looks for context clues to understand the reading.
The surface area of that cube is 8.64 cm
