Lisa, an experienced shipping clerk, can fill a certain order in 10hrs. tom, a new clerk , needs 21 hrs to do the same job. let x represent the number of hrs. it takes lisa and tom to fill the order working together. determine an expression in terms of x that represents how much of the order will be completed in x hours. an expression in terms of x that represents how much of the order will be completed in x hours is
(simplify your answer. use integers or fractions for any numbers in the expression.)