Expression with parentheses..example and non-example

Adam plans to choose a video game from the section of the store where everything is 75% off. he writes the expression d-0.75d to find the sale price of the game if the original price is d dollars. gena correctly writes another expression, 0.25d, that will also find the sale price of the game if the original price is d dollars. use the drop down menus to explain each part of adams and rena's expression

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

Wich statement could be used to explain why the function h(x)= x^3 has an inverse relation that is also a function