What does quantities represent mean

Alexi's restaurant bill is $58, and he wants to leave a 20 percent tip. Which expression represents the total amount that Alexi needs to pay?

Evaluate x+3y when x=2, y-3

suppose that 12 inches of wire cost 72 cents. at the same rate, how many inches of wire can be bought for 36 cents?

What is the simplified expression for - 2a2b + a2 - 5ab + 3ab2 - b2 + 2 (a2b + 2ab) ?

Two containers hold a mixture made out of two chemicals. In container A the two chemicals are in the ratio 1:2. In container B the same chemicals are in the ratio 1:1.

A newspaper reporter wants to know how popular the hobby of bird watching is in the city. He asked people at the local bird refuge if they watched birds as a hobby. Which of the following best explains whether the reporters data is valid or not?

I am very confused on how to figure out if y = 3/4x is proportional?

Alison wants to buy a mountain bike for $339.12. If she saves $28.26 each month, in how many months will she be able to buy the bike?

At 12 o'clock the temperature was 7°C. The temperature decreased by - 20°C. What is the new temperature?

Ashleys rentals charges $27.50 per hour to rent a surfboard and a wetsuit. Darlas surf shop charges $23.25 per hour to rent a surfboard plus $17 extra for a wetsuit.