Let's define the following variable: t = total time it takes to assemble a shelving unit together. We then have the following equation: 1/5 + 1/3 = 1 / t Solving the equation we have: 3t + 5t = 15 8t = 15 t = 1,875 hours Answer: the time it takes for worker A and worker B to assemble a shelving unit together is: t = 1,875 hours