How much of an alloy that is 40% copper should be mixed with 500 ounces of an alloy that is 60% copper in order to get an alloy that is 50% copper?

Jose predicted that he would sell 48 umbrellas. he actually sold 72 umbrellas. what are the values of a and b in the table below? round to the nearest tenth if necessary

Rob spent 25%, percent more time on his research project than he had planned. he spent an extra h hours on the project. which of the following expressions could represent the number of hours rob actually spent on the project? two answers

3x + 4y = 5 x- 3y = -7 solve by substitution