Please help me with these please

It costs 4.25 for 1 pound of roast beef. how much will it cost to purchase 2.5 pounds of roast beef? round to nearest cent

There are 45 questions on your math exam. you answered 810 of them correctly. how many questions did you answer correctly?

Whit h equation best represents this situation the number 98 increased by an unknown number equal to 120