Okay so to do the sqrt(75) you see if there are hidden squares. Split it to be the sqrt(25) and sqrt(3) then simplify. In the end, you get 5sqrt(3). Hope this helps!
Simply present that you would split them up as a factor of two. ( make two lines going either vertically or horizontally. place in varriations, a marble in one line and a marble in the other and then count the leftover
The rate a computer works is 1/time. Working together, you add the rates.
Let new computer be x, old computer be y.
x = y - 7

Rounded to nearest tenth gives:
x = 23 hours
Select all the options because a rectangle can be made of all dimensions.
I believe it’s option #3. hopefully that helps :)