Andrew spent 1 1/6 hours studying for his science exam. he spent another 1 1/2 hours on his history exam. how many total hours did andrew spend studying for his exams?

Achemist has 200 ml of a 10% sucrose solution. she adds x ml of a 40% sucrose solution. the percent concentration, y, of the final mixture is given by the rational function: the chemist needs the concentration of the final mixture to be 30%. how many milliliters of the 40% solution should she add to the 10% solution to get this concentration?

Astick 2 m long is placed vertically at point b. the top of the stick is in line with the top of a tree as seen from point a, which is 3 m from the stick and 30 m from the tree. how tall is the tree?

For what values of the variable x is the expression square root of 7x+14+ square root of 7-x a real number?