How do you solve this type of problem? what does the key represent?

Hiroaki wants to find 3 3/4 - 7/8 explain why he must rename 3 3/4 to do the subtraction.

Afarm that has 4 x 10^2 acres has 1.2 x 10^5 cattle. what is the average number of cattle per acre? write the answer in scientific notation. answere asap

What are the digits that repeat in the smallest sequence of repeating digits in the decimal equivalent of 24/11?