Can someone help me on these stared problems

The graph below shows the amount of money left in the school’s desk fund, f, after d desks have been purchased. for each new desk that is purchased, by how much does the amount of money left in the school’s desk fund decrease?

Two times a number plus three times another number equals 4. three times the first number plus four times the other number is 7. find the numbers

Explain how you divide powers with like bases.discuss why the bases have to be the same.how are these rules similar to the rules for multiplying powers with like bases.