Math help math world problem

alberto invests his $90 for 2 years at r% per year simple interest. at the end of 2 years the amount of money he has is $99. calculate the value of r%.

carlos buys a box of 50 oranges for $8. he sells all the oranges for 25 cents each. calculate the profit he makes.

As of mid-2016, the world's population was about 7.4 billion people. The population of the United States was 324 million.The area of a certain city is 302 square miles. If in mid-2016 every person... more

please help me! this is an important test.

one day a store sold 36 sweatshirts. White ones cost $9.95 and yellow ones cost $13.50 . In all $422.10 worth of sweatshirts were sold . how many of each color were sold ?

Otto and Kurt are going snowboarding. Otto sets off down a 2000 m run. Kurt starts 30 seconds after Otto (taking longer to strap on his board, and untuck his shirt to look cool.) He decides to go... more

need help now

Jade buys a 500g bag of beads at a market.  Each bead has a mass of 0.48g.  Which of these is the best estimate for the number of beads in the 500g bag? a) 100 b) 250 c) 1000 d) 2500

A building is 1 ft from a 10-ft fence that surrounds the property. A worker wants to wash a window in the building 13 ft from the ground. He plans to place a ladder over the fence so it rests... more

The length of a rectangle is 5 inches more than the width. The perimeter is 26 inches. Find the length and the width.

Susan left the airport and drove east.Cody left three hours later driving 36 mphfaster in an effort to catch up to her. Aftertwo hours Cody finally caught up. Whatwas Susan's average speed?

need to know how to solve it 

cant figure this question out, any help would be greatly appreciated.

41 times the difference between a number and 10 is equal to the number plus −42

  I am having trouble figuring out this math problem. Could anyone explain on how to get the answer?

The time required for a skilled worker to produce x shirts is given by the function T(x) = 4x + 2, where T is measured in hours. The salary the she is paid is given by the function S(T) = 15T,... more